Add TYPE_CHECKING builtin

Author: methane

Python/bltinmodule.c

@@ -3407,6 +3407,7 @@ _PyBuiltin_Init(PyInterpreterState *interp)
     SETBUILTIN("tuple",                 &PyTuple_Type);
     SETBUILTIN("type",                  &PyType_Type);
     SETBUILTIN("zip",                   &PyZip_Type);
+    SETBUILTIN("TYPE_CHECKING",         Py_False);
     debug = PyBool_FromLong(config->optimization_level == 0);
     if (PyDict_SetItemString(dict, "__debug__", debug) < 0) {
         Py_DECREF(debug);