Bypass Python tests throwing base classes as exceptions for -builtin

Throwing builtin classes as exceptions is not supported

Examples/test-suite/threads_exception.i

@@ -52,4 +52,10 @@ public:
      return 1;
   }
 };
+
+#ifdef SWIGPYTHON_BUILTIN
+bool is_python_builtin() { return true; }
+#else
+bool is_python_builtin() { return false; }
+#endif
 %}