PCH recompilation not working for clang
Tested !3553 (merged).
PCH recompilation does not seem to work properly with clang, it always fails the first time after the pch header file has been touched:
$ ninja -v
[0/2] /usr/bin/cmake -P CMakeFiles/VerifyGlobs.cmake
[1/3] /usr/bin/clang++ -g -std=gnu++2a -Winvalid-pch -x c++-header -include CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx -MD -MT CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch -MF CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch.d -o CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch -c CMakeFiles/test.dir/cmake_pch.hxx.cxx
FAILED: CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch
/usr/bin/clang++ -g -std=gnu++2a -Winvalid-pch -x c++-header -include CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx -MD -MT CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch -MF CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch.d -o CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch -c CMakeFiles/test.dir/cmake_pch.hxx.cxx
fatal error: file 'pch.h' has been modified since the precompiled header 'CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch' was built
note: please rebuild precompiled header 'CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch'
1 error generated.
$ ninja -v
[0/2] /usr/bin/cmake -P CMakeFiles/VerifyGlobs.cmake
[1/3] /usr/bin/clang++ -g -std=gnu++2a -Winvalid-pch -x c++-header -include CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx -MD -MT CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch -MF CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch.d -o CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx.gch -c CMakeFiles/test.dir/cmake_pch.hxx.cxx
[2/3] /usr/bin/clang++ -g -std=gnu++2a -Winvalid-pch -include CMakeFiles/test.dir/CMakeFiles/test.dir/cmake_pch.hxx -MD -MT CMakeFiles/test.dir/main.cpp.o -MF CMakeFiles/test.dir/main.cpp.o.d -o CMakeFiles/test.dir/main.cpp.o -c ../main.cpp
[3/3] : && /usr/bin/clang++ -g CMakeFiles/test.dir/main.cpp.o -o bin/test && :