While trying to build zero jvm variant on macosx-x64, I ran into the following build error during building of jdk (make jdk):
=== Output from failing command(s) repeated here ===
* For target support_native_java.base_libfallbackLinker_fallbackLinker.o:
.../open/src/java.base/share/native/libfallbackLinker/fallbackLinker.c:156:8: error: unused variable 'result' [-Werror,-Wunused-variable]
  jint result = (*VM)->AttachCurrentThreadAsDaemon(VM, (void**) &env, NULL);
       ^
1 error generated.

To reproduce the above:
- configure to build zero jvm variant with the --with-jvm-variants=zero option on macosx-x64
  (note: I haven't tried macosx-aarch64)
- build jdk
  make jdk