[lld] [lld][ELF] Simplify handleLibcall. NFC (PR #78659)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay approved this pull request.

Thanks! I think this opportunity is enabled by my previous change removing LazyArchive https://reviews.llvm.org/D119074

https://github.com/llvm/llvm-project/pull/78659