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

[via llvm-commits]

================
@@ -52,13 +52,16 @@ computeAliasingInstructions(const LLVMState &State, const Instruction *Instr,
       continue;
     if (OtherOpcode == Instr->Description.getOpcode())
       continue;
+    if (!State.getExegesisTarget().checkOpcodeSupported(
----------------
AnastasiyaChernikova wrote:

This is useful contribution, but it too small for a new patch, let's leave it here

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