[lld] [ELF] Add target-specific relocation scanning for x86 (PR #178846)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

sorry, I missed https://github.com/llvm/llvm-project/pull/178846#issuecomment-4033125619, only saw the comment after

we can exclude msan symbols from `-u`. it would be nice if there were some diagnostic saying that `-u tls_var` is unsupported rather than an arbitrary relocation overflow that doesn't make sense

https://github.com/llvm/llvm-project/pull/178846