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

[Alex Bradbury via llvm-commits]

asb wrote:

> > @MaskRay @asb Are we happy w/ this patch? I think I've addressed most of the concerns raised thus far, but I want try and finish the attributes patches this week if possible, since I'm back from EuroLLVM + vacation.
> 
> I am sorry it took a long time for me to notice the discussion and make some comments about the linker code. While I appreciate the LGTM, given the number of linker comments I had to give, landing this 7 hours after LGTM feels a bit rushed. (If asb's LGTM was given on the day you commented, I'd certainly not oppose as it was my fault not noticing the change in 3 days.)

Sorry for that @MaskRay. I should have given an LGTM conditional on you or another lld dev explicitly lgtming the linker code. I think given jrtc27 had been involved in the thread and a discussion thread with you was mentioned I'd misjudged the level of attention this had got already from lld folks - so my bad.

https://github.com/llvm/llvm-project/pull/84597