[BOLT][RISCV] Handle EH_LABEL operands (#68998)

Fixes the `runtime/exceptions-no-pie.cpp` test on RISC-V.

Author: mtvec

bolt/lib/Target/RISCV/RISCVMCPlusBuilder.cpp

@@ -303,6 +303,7 @@ class RISCVMCPlusBuilder : public MCPlusBuilder {
     default:
       return false;
     case RISCV::C_J:
+    case TargetOpcode::EH_LABEL:
       OpNum = 0;
       return true;
     case RISCV::AUIPC: