[clang] [clang][modules] HeaderSearch::MarkFileModuleHeader creates extra HeaderFileInfo, breaks PCM reuse (PR #89005)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

I don't really know a great way to write a test for this. If someone could point me at a similar existing test or has an idea how to write a new test that would be much appreciated.

https://github.com/llvm/llvm-project/pull/89005