[clang] [llvm] Revert "[Sema] Mark alias/ifunc targets used and consider mangled names" (PR #88919)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Thanks. 1c2afbae9af22b58190c10e3517242d01d89d612 is a codegen test of this involved llvm-libc pattern which would also catch the bug.

https://github.com/llvm/llvm-project/pull/88919