Error message:
=== Output from failing command(s) repeated here ===
* For target hotspot_variant-server_libjvm_objs_g1CollectedHeap.o:
In file included from /Source/jdk11u-dev/src/hotspot/cpu/x86/assembler_x86.inline.hpp:30:0,
                 from /Source/jdk11u-dev/src/hotspot/share/asm/assembler.inline.hpp:30,
                 from /Source/jdk11u-dev/src/hotspot/share/precompiled/precompiled.hpp:32:
/Source/jdk11u-dev/src/hotspot/share/code/codeCache.hpp: In member function 'void G1CollectedHeap::complete_cleaning(BoolObjectClosure*, bool)':
/Source/jdk11u-dev/src/hotspot/share/code/codeCache.hpp:377:5: error: 'iter.CodeBlobIterator<CompiledMethod, CompiledMethodFilter>::_code_blob' may be used uninitialized in this function [-Werror=maybe-uninitialized]
     if (_code_blob == NULL) {
     ^~
/Source/jdk11u-dev/src/hotspot/share/gc/g1/g1CollectedHeap.cpp:3355:28: note: 'iter.CodeBlobIterator<CompiledMethod, CompiledMethodFilter>::_code_blob' was declared here
     CompiledMethodIterator iter = CompiledMethodIterator();
                            ^~~~
cc1plus: all warnings being treated as errors

* All command lines available in /Source/jdk11u-dev/build/linux-x86_64-normal-server-release/make-support/failure-logs.
=== End of repeated output ===

And

=== Output from failing command(s) repeated here ===
* For target hotspot_variant-server_libjvm_objs_genCollectedHeap.o:
/Source/jdk11u-dev/src/hotspot/share/gc/shared/genCollectedHeap.cpp: In member function 'ScratchBlock* GenCollectedHeap::gather_scratch(Generation*, size_t)':
/Source/jdk11u-dev/src/hotspot/share/gc/shared/genCollectedHeap.cpp:1147:18: error: 'smallest_ptr' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   ScratchBlock **smallest_ptr, *smallest;
                  ^~~~~~~~~~~~
cc1plus: all warnings being treated as errors

* All command lines available in /Source/jdk11u-dev/build/linux-x86_64-normal-server-release/make-support/failure-logs.
=== End of repeated output ===

more info:
The build can success if use --disable-warnings-as-errors