[lld] [LLD][SPARC] Implement enough functionality to run non-trivial 64-bit programs (PR #137919)

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

Aside from tests, this would also benefit from being multiple commits rather than one big change, as it's moving lots of things around and touching common code.

https://github.com/llvm/llvm-project/pull/137919