When using the configure flag --enable-jvm-feature-opt-size (linux x86_64 opt build, gcc 11 devkit) we run into this error after the recent PCH related changes :

cc1plus: error: /build_optsize/hotspot/variant-server/libjvm/objs/precompiled/precompiled.hpp.gch: not used because `__OPTIMIZE_SIZE__' not defined [-Werror=invalid-pch]

+ exit 1
gmake[3]: *** [lib/CompileJvm.gmk:170: /build_optsize/hotspot/variant-server/libjvm/objs/allocation.o] Error 1

Please note that allocation.cpp is currently in the list of OPT_SPEED_SRC files (means - files to be optimized for speed even in case of SIZE optimization) :
https://github.com/openjdk/jdk/blob/master/make/hotspot/lib/JvmFeatures.gmk#L196

Same issue can be observed on Windows x86_64 (VS2022 used).