Tools summary:
* Environment: cygwin version 3.1.7(0.340/5/3), 2020-08-22 17:48. Windows version 10.0.18363.1082. Root at /cygdrive/c/cygwin64
* Boot JDK: openjdk version "14.0.1-internal" 2020-04-14 OpenJDK Runtime Environment (build 14.0.1-internal+0-adhoc..build) OpenJDK 64-Bit Server VM (build 14.0.1-internal+0-adhoc..build, mixed mode, sharing) (at /cygdrive/c/buildbot/jdks/jdk14)
* Toolchain: microsoft (Microsoft Visual Studio 2017)
* C Compiler: Version 19.16.27039 (at /cygdrive/c/progra~2/micros~1/2017/commun~1/vc/tools/msvc/1416~1.270/bin/hostx86/x64/cl)
* C++ Compiler: Version 19.16.27039 (at /cygdrive/c/progra~2/micros~1/2017/commun~1/vc/tools/msvc/1416~1.270/bin/hostx86/x64/cl)

c:/buildbot/worker/build-jdkX-windows/build/src/hotspot/share/runtime/flags/jvmFlagLookup.cpp(54): error C2220: warning treated as error - no 'object' file generated
c:/buildbot/worker/build-jdkX-windows/build/src/hotspot/share/runtime/flags/jvmFlagLookup.cpp(54): warning C4307: '*': integral constant overflow
make[3]: *** [lib/CompileJvm.gmk:143: /cygdrive/c/buildbot/worker/build-jdkX-windows/build/build/windows-x86_64-server-fastdebug/hotspot/variant-server/libjvm/objs/jvmFlagLookup.obj] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [make/Main.gmk:259: hotspot-server-libs] Error 2