message: Fix backend string type.
diff: @@ -868,7 +868,7 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
  baseline: true,
  msm: msm,
  base: instance.module.runnable_module.get_code().unwrap().as_ptr() as usize,
  - backend: options.backend.to_string().to_owned(),
  + backend: options.backend.to_string(),
  runnable_module: instance.module.runnable_module.clone(),
  });
  true
  