cmake-gui: Fix error status when interrupted.

Sometimes it wasn't returning an error and one could continue
with the generate generate as if no errors occurred, and even
with an incomplete configure step.

Source/cmSystemTools.h

@@ -92,7 +92,8 @@ public:
   static bool GetErrorOccuredFlag()
     {
       return cmSystemTools::s_ErrorOccured ||
-        cmSystemTools::s_FatalErrorOccured;
+        cmSystemTools::s_FatalErrorOccured ||
+        GetInterruptFlag();
     }
   ///! If this is set to true, cmake stops processing commands.
   static void SetFatalErrorOccured()