ADDITIONAL SYSTEM INFORMATION :
- Windows 10
- Javafx - tag 15+9 (checked out from https://github.com/openjdk/jfx/tree/15%2B9)
- Java 15 (installed on Windows)
- Ant 1.10.5 (installed on Windows)
- CMake 3.19.5 (installed on Windows)
- Visual Studio 2017 community edition
- CygWin (installed on Windows) with the following packages:
  - bison 3.0.4-1
  - flex 2.6.4-2
  - gcc-g++ 10.2.0-1
  - git 2.30.0-1
  - gperf 3.1-1
  - make 4.3-1
  - makedepend 1.0.6-1
  - openssh 8.4p1-2
  - perl 5.32.1-1
  - python27 2.7.18-4
  - ruby 2.6.4-1
  - unzip 6.0-17
  - zip 3.0-12

A DESCRIPTION OF THE PROBLEM :
I've followed all of the steps on:
https://wiki.openjdk.java.net/display/OpenJFX/Building+OpenJFX

Following libraries were used:
- Javafx - tag 15+9 (checked out from https://github.com/openjdk/jfx/tree/15%2B9)
- Java 15 (installed on Windows)
- Ant 1.10.5 (installed on Windows)
- CMake 3.19.5 (installed on Windows)
- Visual Studio 2017 community edition
- CygWin (installed on Windows) with the following packages:
  - bison 3.0.4-1
  - flex 2.6.4-2
  - gcc-g++ 10.2.0-1
  - git 2.30.0-1
  - gperf 3.1-1
  - make 4.3-1
  - makedepend 1.0.6-1
  - openssh 8.4p1-2
  - perl 5.32.1-1
  - python27 2.7.18-4
  - ruby 2.6.4-1
  - unzip 6.0-17
  - zip 3.0-12
  
Environment variables are set properly:
JAVA_HOME="C:\\Program Files\\jdk-15\\"
MSVC_VER="14.16.27023"
VS150COMNTOOLS="C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Auxiliary\\Build"

JFX/build/windows_tools.properties was successfully created.

Following properties in gradle.properties are set like:
COMPILE_WEBKIT = true
CONF = DebugNative

After everything is setup I try to run:
./gradlew --info --console=plain --stacktrace

Instead of successful build I see:
Successfully started process 'command 'perl''
+ cmake --build C:/jfx/modules/javafx.web/build/win/Debug --config Debug --
[0/3018] Generate bindings (WebCoreBindings)
[1/3018] Linking CXX executable bin\LLIntOffsetsExtractor.exe
FAILED: bin/LLIntOffsetsExtractor.exe
cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --intdir=Source\JavaScriptCore\CMakeFiles\LLIntOffsetsExtract
or.dir --rc="C:\Program Files (x86)\Windows Kits\10\bin\10.0.17763.0\x64\rc.exe" --mt="C:\Program Files (x86)\Windows Kits\10\bin\10.0.
17763.0\x64\mt.exe" --manifests -- "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\bin\Hostx6
4\x64\link.exe" /nologo Source\JavaScriptCore\CMakeFiles\LLIntOffsetsExtractor.dir\llint\LLIntOffsetsExtractor.cpp.obj /out:bin\LLIntO
ffsetsExtractor.exe /implib:lib\LLIntOffsetsExtractor.lib /pdb:bin\LLIntOffsetsExtractor.pdb /version:0.0 /machine:x64 /DEBUG /OPT:ICF
/OPT:REF /OPT:NOREF /OPT:NOICF /INCREMENTAL:NO /debug /INCREMENTAL /INCREMENTAL:NO /subsystem:console lib\WTF.lib lib\icudata.lib li
b\icui18n.lib lib\icuuc.lib "C:\Program Files\jdk-15\lib\jvm.lib" winmm.lib dbghelp.lib kernel32.lib user32.lib gdi32.lib winspool
.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd ."
LINK Pass 1: command "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\bin\Hostx64\x64\link.exe
/nologo Source\JavaScriptCore\CMakeFiles\LLIntOffsetsExtractor.dir\llint\LLIntOffsetsExtractor.cpp.obj /out:bin\LLIntOffsetsExtractor.e
xe /implib:lib\LLIntOffsetsExtractor.lib /pdb:bin\LLIntOffsetsExtractor.pdb /version:0.0 /machine:x64 /DEBUG /OPT:ICF /OPT:REF /OPT:NOR
EF /OPT:NOICF /INCREMENTAL:NO /debug /INCREMENTAL /INCREMENTAL:NO /subsystem:console lib\WTF.lib lib\icudata.lib lib\icui18n.lib lib\ic
uuc.lib C:\Program Files\jdk-15\lib\jvm.lib winmm.lib dbghelp.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib
oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:Source\JavaScriptCore\CMakeFiles\LLIntOffsetsExtractor.dir/inte
rmediate.manifest Source\JavaScriptCore\CMakeFiles\LLIntOffsetsExtractor.dir/manifest.res" failed (exit code 1120) with the following o
utput:
   Creating library lib\LLIntOffsetsExtractor.lib and object lib\LLIntOffsetsExtractor.exp
LLIntOffsetsExtractor.cpp.obj : error LNK2019: unresolved external symbol "bool __cdecl WTF::isMainThreadInitialized(void)" (?isMainThr
eadInitialized@WTF@@YA_NXZ) referenced in function "protected: __cdecl WTF::RefCountedBase::RefCountedBase(void)" (??0RefCountedBase@WT
F@@IEAA@XZ)
WTF.lib(JSONValues.cpp.obj) : error LNK2001: unresolved external symbol "bool __cdecl WTF::isMainThreadInitialized(void)" (?isMainThrea
dInitialized@WTF@@YA_NXZ)
WTF.lib(MediaTime.cpp.obj) : error LNK2001: unresolved external symbol "bool __cdecl WTF::isMainThreadInitialized(void)" (?isMainThread
Initialized@WTF@@YA_NXZ)
WTF.lib(CString.cpp.obj) : error LNK2001: unresolved external symbol "bool __cdecl WTF::isMainThreadInitialized(void)" (?isMainThreadIn
itialized@WTF@@YA_NXZ)
bin\LLIntOffsetsExtractor.exe : fatal error LNK1120: 1 unresolved externals
ninja: build stopped: subcommand failed.

> Task :web:compileNativeWin FAILED
:web:compileNativeWin (Thread[Execution worker for ':' Thread 11,5,main]) completed. Took 5.27 secs.

FAILURE: Build failed with an exception.

* Where:
Build file 'C:\jfx\build.gradle' line: 3445

* What went wrong:
Execution failed for task ':web:compileNativeWin'.
> Process 'command 'perl'' finished with non-zero exit value 1

* Try:
Run with --debug option to get more log output. Run with --scan to get full insights.

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':web:compileNativeWin'.
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.lambda$executeIfValid$1(ExecuteActionsTaskExecuter.java:2
05)
        at org.gradle.internal.Try$Failure.ifSuccessfulOrElse(Try.java:263)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeIfValid(ExecuteActionsTaskExecuter.java:203)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:184)
        at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:114)
        at org.gradle.api.internal.tasks.execution.FinalizePropertiesTaskExecuter.execute(FinalizePropertiesTaskExecuter.java:46)
        at org.gradle.api.internal.tasks.execution.ResolveTaskExecutionModeExecuter.execute(ResolveTaskExecutionModeExecuter.java:62)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:57)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:56)
        at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:36)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.executeTask(EventFiringTaskExecuter.java:77)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:55)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:52)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecu
tor.java:416)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecu
tor.java:406)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.call(DefaultBuildOperationExecutor.java:102)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.call(DelegatingBuildOperationExecutor.java:36)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:52)
        at org.gradle.execution.plan.LocalTaskNodeExecutor.execute(LocalTaskNodeExecutor.java:41)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:37
2)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:35
9)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGrap
h.java:352)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGrap
h.java:338)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.lambda$run$0(DefaultPlanExecutor.java:127)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:191)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:182)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:124)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
Caused by: org.gradle.process.internal.ExecException: Process 'command 'perl'' finished with non-zero exit value 1
        at org.gradle.process.internal.DefaultExecHandle$ExecResultImpl.assertNormalExitValue(DefaultExecHandle.java:417)
        at org.gradle.process.internal.DefaultExecAction.execute(DefaultExecAction.java:38)
        at org.gradle.process.internal.DefaultExecActionFactory.exec(DefaultExecActionFactory.java:156)
        at org.gradle.groovy.scripts.DefaultScript.exec(DefaultScript.java:249)
        at jdk.internal.reflect.GeneratedMethodAccessor402.invoke(Unknown Source)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at org.gradle.internal.metaobject.BeanDynamicObject$GroovyObjectAdapter.invokeOpaqueMethod(BeanDynamicObject.java:583)
        at org.gradle.internal.metaobject.BeanDynamicObject$MetaClassAdapter.invokeMethod(BeanDynamicObject.java:510)
        at org.gradle.internal.metaobject.BeanDynamicObject.tryInvokeMethod(BeanDynamicObject.java:195)
        at org.gradle.internal.metaobject.ConfigureDelegate.invokeMethod(ConfigureDelegate.java:77)
        at build_4rsf6oo4eh8rcq3x9l8zfk58w$_run_closure22$_closure269$_closure277$_closure282.doCall(C:\jfx\build.gradle:3445)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at org.gradle.api.internal.AbstractTask$ClosureTaskAction.execute(AbstractTask.java:670)
        at org.gradle.api.internal.AbstractTask$ClosureTaskAction.execute(AbstractTask.java:643)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.run(ExecuteActionsTaskExecuter.java:568)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecu
tor.java:402)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecu
tor.java:394)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:92)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:553)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:536)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.access$300(ExecuteActionsTaskExecuter.java:109)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$TaskExecution.executeWithPreviousOutputFiles(ExecuteActio
nsTaskExecuter.java:276)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$TaskExecution.execute(ExecuteActionsTaskExecuter.java:265
)
        at org.gradle.internal.execution.steps.ExecuteStep.lambda$execute$1(ExecuteStep.java:33)
        at org.gradle.internal.execution.steps.ExecuteStep.execute(ExecuteStep.java:33)
        at org.gradle.internal.execution.steps.ExecuteStep.execute(ExecuteStep.java:26)
        at org.gradle.internal.execution.steps.CleanupOutputsStep.execute(CleanupOutputsStep.java:67)
        at org.gradle.internal.execution.steps.CleanupOutputsStep.execute(CleanupOutputsStep.java:36)
        at org.gradle.internal.execution.steps.ResolveInputChangesStep.execute(ResolveInputChangesStep.java:49)
        at org.gradle.internal.execution.steps.ResolveInputChangesStep.execute(ResolveInputChangesStep.java:34)
        at org.gradle.internal.execution.steps.CancelExecutionStep.execute(CancelExecutionStep.java:43)
        at org.gradle.internal.execution.steps.TimeoutStep.executeWithoutTimeout(TimeoutStep.java:73)
        at org.gradle.internal.execution.steps.TimeoutStep.execute(TimeoutStep.java:54)
        at org.gradle.internal.execution.steps.CatchExceptionStep.execute(CatchExceptionStep.java:34)
        at org.gradle.internal.execution.steps.CreateOutputsStep.execute(CreateOutputsStep.java:44)
        at org.gradle.internal.execution.steps.SnapshotOutputsStep.execute(SnapshotOutputsStep.java:54)
        at org.gradle.internal.execution.steps.SnapshotOutputsStep.execute(SnapshotOutputsStep.java:38)
        at org.gradle.internal.execution.steps.BroadcastChangingOutputsStep.execute(BroadcastChangingOutputsStep.java:49)
        at org.gradle.internal.execution.steps.CacheStep.executeWithoutCache(CacheStep.java:159)
        at org.gradle.internal.execution.steps.CacheStep.execute(CacheStep.java:72)
        at org.gradle.internal.execution.steps.CacheStep.execute(CacheStep.java:43)
        at org.gradle.internal.execution.steps.StoreExecutionStateStep.execute(StoreExecutionStateStep.java:44)
        at org.gradle.internal.execution.steps.StoreExecutionStateStep.execute(StoreExecutionStateStep.java:33)
        at org.gradle.internal.execution.steps.RecordOutputsStep.execute(RecordOutputsStep.java:38)
        at org.gradle.internal.execution.steps.RecordOutputsStep.execute(RecordOutputsStep.java:24)
        at org.gradle.internal.execution.steps.SkipUpToDateStep.executeBecause(SkipUpToDateStep.java:92)
        at org.gradle.internal.execution.steps.SkipUpToDateStep.lambda$execute$0(SkipUpToDateStep.java:85)
        at org.gradle.internal.execution.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:55)
        at org.gradle.internal.execution.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:39)
        at org.gradle.internal.execution.steps.ResolveChangesStep.execute(ResolveChangesStep.java:76)
        at org.gradle.internal.execution.steps.ResolveChangesStep.execute(ResolveChangesStep.java:37)
        at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsFinishedStep.execute(MarkSnapshottingInputsFinishedStep.jav
a:36)
        at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsFinishedStep.execute(MarkSnapshottingInputsFinishedStep.jav
a:26)
        at org.gradle.internal.execution.steps.ResolveCachingStateStep.execute(ResolveCachingStateStep.java:94)
        at org.gradle.internal.execution.steps.ResolveCachingStateStep.execute(ResolveCachingStateStep.java:49)
        at org.gradle.internal.execution.steps.CaptureStateBeforeExecutionStep.execute(CaptureStateBeforeExecutionStep.java:79)
        at org.gradle.internal.execution.steps.CaptureStateBeforeExecutionStep.execute(CaptureStateBeforeExecutionStep.java:53)
        at org.gradle.internal.execution.steps.ValidateStep.execute(ValidateStep.java:74)
        at org.gradle.internal.execution.steps.SkipEmptyWorkStep.lambda$execute$2(SkipEmptyWorkStep.java:78)
        at org.gradle.internal.execution.steps.SkipEmptyWorkStep.execute(SkipEmptyWorkStep.java:78)
        at org.gradle.internal.execution.steps.SkipEmptyWorkStep.execute(SkipEmptyWorkStep.java:34)
        at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsStartedStep.execute(MarkSnapshottingInputsStartedStep.java:
39)
        at org.gradle.internal.execution.steps.LoadExecutionStateStep.execute(LoadExecutionStateStep.java:40)
        at org.gradle.internal.execution.steps.LoadExecutionStateStep.execute(LoadExecutionStateStep.java:28)
        at org.gradle.internal.execution.impl.DefaultWorkExecutor.execute(DefaultWorkExecutor.java:33)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeIfValid(ExecuteActionsTaskExecuter.java:192)
        ... 30 more


* Get more help at https://help.gradle.org

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.3/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 8s
57 actionable tasks: 10 executed, 47 up-to-date

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Just setup the environment as described in description and run a build.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Successful build.
ACTUAL -
Failed build.

CUSTOMER SUBMITTED WORKAROUND :
No workaround has been found.

FREQUENCY : always