[lld] [llvm] Reapply "[RISCV] Support RISCV Atomics ABI attributes (#84597)" (PR #90266)

[Philip Reames via llvm-commits]

preames wrote:

Since we're going to have the flag emission under a flag anyways, can we separate the LLD part into a separate review?  Doing so would seem to unblock the compiler side changes, and let the LLD review comments move at their own pace.  

https://github.com/llvm/llvm-project/pull/90266