[clang] Reapply "[Clang] Take libstdc++ into account during GCC detection" #154368 (PR #154487)

[Frederik Harwath via cfe-commits]

frederik-h wrote:

@MaskRay This fixes the two issues that you mentioned in your [comment](https://github.com/llvm/llvm-project/pull/145056#issuecomment-3204637760) on the original PR. I have checked the build bot errors and I did not see any other issues. This means the patch can probably be reapplied, right?

https://github.com/llvm/llvm-project/pull/154487