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

[Craig Topper via llvm-commits]

topperc wrote:

@AnastasiyaChernikova The new memory functionality to the base of llvm-exegesis needs to be mentioned in the commit PR description. It really should be in a separate PR that is separate from enabling basic RISC-V support. It is hard to justify that being in the first RISC-V patch when it is new functionality that other targets don't have.

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