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

[Tom Honermann via cfe-commits]

https://github.com/tahonermann approved this pull request.

This looks great to me. Thank you for working on this!

Please give @MaskRay a chance to comment on this before merging it.

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