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

[Piotr Zegar via cfe-commits]

PiotrZSL wrote:

No need for release notes as this realpath stuff were added in this release anyway. So this is just a fix for degradation.

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