[clang] [Clang][Lex] Warn on trailing whitespace in #include filenames (PR #167163)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman requested changes to this pull request.

I believe the consensus on the issue was to extend `-Wnonportable-include-path` rather than introduce a new diagnostic group.

https://github.com/llvm/llvm-project/issues/96064#issuecomment-2180546907

https://github.com/llvm/llvm-project/pull/167163