[clang] [clang] Implement -Wmissing-include-dirs (PR #94827)

[Braden Helmer via cfe-commits]

bradenhelmer wrote:

> Do you have access to press the "Squash and merge" button, or should I do it?

You'll have to, i dont have access yet, thx

https://github.com/llvm/llvm-project/pull/94827