message: OpExtInstImport isn't expected to happen during debugging
diff: @@ -1504,6 +1504,7 @@ void ThreadState::StepNext(ShaderDebugState *state,
  case Op::MemberName:
  case Op::String:
  case Op::Extension:
  + case Op::ExtInstImport:
  case Op::MemoryModel:
  case Op::EntryPoint:
  case Op::ExecutionMode:
  