[clang] [clang][Modules] Reland fixing unexpected warnings triggered by a PCH and a mod… (PR #177078)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

> > The revised PR now has a test case that works well on swift/next. The test now passes absolute paths to -include-pch.
> 
> You mentioned to me offline, that you would resolve the underlying bug before moving forward on this patch. What happened there? Changing the test case does nothing for handling the underlying assert-based crash downstream on what seems like reasonable usage.

I think that's <https://github.com/llvm/llvm-project/pull/180065>?

https://github.com/llvm/llvm-project/pull/177078