[Flang][CI] Merge CI rejects any change to llvm/Support/Compiler.h

[kikairoya]

I noticed a build failure after making a change to llvm/include/llvm/Support/Compiler.h .
#143222 (comment)

The build log shows the following error:

fatal error: file 'C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\llvm\include\llvm\Support\Compiler.h' has been modified since the precompiled header 'C:/Users/tcwg/llvm-worker/flang-arm64-windows-msvc/build/tools/flang/lib/Parser/CMakeFiles/FortranParser.dir/./cmake_pch.cxx.pch' was built: size changed (was 27102, now 27125)

It appears that the build system does not properly detect and rebuild the precompiled header when one of its dependencies is updated.

[kikairoya]

The same problem appeared at https://lab.llvm.org/buildbot/#/builders/207/builds/2188 , but repaired between https://lab.llvm.org/buildbot/#/builders/207/builds/2262 and https://lab.llvm.org/buildbot/#/builders/207/builds/2263 .

[kikairoya]

https://lab.llvm.org/buildbot/#/builders/207/builds/2664
Although the CI has recovered, CMakeLists.txt hasn't been updated, so the same issue might still occur.