[llvm] [RISCV] Teach .option arch to support experimental extensions. (PR #89727)

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

> > Also, does this obey -menable-experimental-extensions?
> 
> IMO, I prefer this feature depends on `-menable-experimental-extensions`.

Yes, I believe it should. My question is whether it currently does, especially given I don’t believe your current patch is testing it?

https://github.com/llvm/llvm-project/pull/89727