[lld] [LLD][COFF] add __lld_buildid symbol. (PR #74652)

[Petr Hosek via llvm-commits]

petrhosek wrote:

Can we avoid `lld` in the name and call it just `__buildid`? I'm worried that calling it `__lld_buildid` might discourage other COFF linkers from adopting it.

https://github.com/llvm/llvm-project/pull/74652