[clang-tools-extra] [clang-tidy] Optimize realpath in readability-identifier-naming (PR #92659)

[Julian Schmidt via cfe-commits]

https://github.com/5chmidti approved this pull request.

This halves the time clang-tidy takes to run this check on `IdentifierNamingCheck.cpp` for me :)

Maybe add a release note?


https://github.com/llvm/llvm-project/pull/92659