observe "stopped" after Cygwin init (which is itself uninterruptible);

--- a/src/Pure/Tools/main.scala	Sat Sep 07 17:32:55 2013 +0200
+++ b/src/Pure/Tools/main.scala	Sat Sep 07 17:43:13 2013 +0200
@@ -132,6 +132,11 @@
         }
       }
       catch { case exn: Throwable => exit_error(exn) }
+
+      if (system_dialog.stopped) {
+        system_dialog.return_code(130)
+        system_dialog.join_exit
+      }
     }
 
     build