Fix error

src/librustc_driver/driver.rs

@@ -71,6 +71,7 @@ pub fn compile_input(sess: &Session,
                      output: &Option<PathBuf>,
                      addl_plugins: Option<Vec<String>>,
                      control: &CompileController) -> CompileResult {
+    use rustc_trans::back::write::OngoingCrateTranslation;
     macro_rules! controller_entry_point {
         ($point: ident, $tsess: expr, $make_state: expr, $phase_result: expr) => {{
             let state = &mut $make_state;