[clang] [Driver] Ignore non-clang pch files when -include a.h probes a.h.gch (PR #69204)

[via cfe-commits]

zmodem wrote:

Please take a look.

This has the benefit of fixing users broken by gcc-generated .gch files without having to wait a release cycle for deprecation, while at the same time not breaking users relying clang performing these probes at all.

cc folks from the previous pr:
@MaskRay @jansvoboda11 @nico @tahonermann @dwblaikie 

https://github.com/llvm/llvm-project/pull/69204