Add a test that we're not enabling the GIL.

Author: jamadden

src/greenlet/tests/test_greenlet.py

@@ -1349,5 +1349,13 @@ def test_reentrant_switch_run_callable_has_del(self):
             output
         )
 
+class TestModule(TestCase):
+
+    def test_no_gil_on_free_threaded(self):
+        if RUNNING_ON_FREETHREAD_BUILD:
+            self.assertFalse(sys._is_gil_enabled())
+        else:
+            self.assertTrue(sys._is_gil_enabled())
+
 if __name__ == '__main__':
     unittest.main()