[clang] [modules] Add diagnostic about performed input file validation when encounter unrecoverable changed input file. (PR #180899)

[Cyndy Ishida via cfe-commits]

https://github.com/cyndyishida commented:

Sorry, I have a lot of bike shedding comments, but thank you for adding this, Volodymyr!

https://github.com/llvm/llvm-project/pull/180899