[llvm] [Exegesis][RISCV] Add RISCV support for llvm-exegesis (PR #89047)

[Craig Topper via llvm-commits]

topperc wrote:

> @boomanaiden154 @gchatelet @mshockwave @topperc @michaelmaitland @legrosbuffle @wangpc-pp @dtcxzyw @keeranroth I answered all the comments, please take a look. Maybe I could merge all the commits into one?

This comment has not been addressed https://github.com/llvm/llvm-project/pull/89047#issuecomment-2484180781

https://github.com/llvm/llvm-project/pull/89047