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

[Paul Kirth via llvm-commits]

ilovepi wrote:

Sorry for the delay on this. I lost track of this w/ other priorities. I think the new implementation does what everyone wants it to do: guard codegen w/ the `cl::opt`. It's less clear to me what we'll do w/ enabling trailing fence by default, w/o the attributes on by default, but that's orthogonal to this.

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