[clang] [clang][lex] Fix lexing malformed pragma within include directive (PR #138165)

[Stefan Weigl-Bosker via cfe-commits]

sweiglbosker wrote:

> Thanks for the fix! Given the nature of the issue, I would probably introduce a new test file rather than modify an existing one. But I think it should live in `clang/test/Preprocessor`.

Just added a small test. Looks good to you?

https://github.com/llvm/llvm-project/pull/138165