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

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

> getExistingFileInfo(, /*WantExternal=*/false)

Until [recently](https://github.com/llvm/llvm-project/pull/87848) that function still consulted `ExternalSource` for `HeaderFileInfo` that `IsValid && !External && !Resolved`. Maybe you want to try the new `getExistingLocalFileInfo()`?

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