Update ll_builder.py

Author: BobTheBuidler

mypyc/irbuild/ll_builder.py

@@ -8,7 +8,9 @@
 
 import sys
 from collections.abc import Sequence
-from typing import Callable, Final, Optional, TypeGuard
+from typing import Callable, Final, Optional
+
+from typing_extensions import TypeGuard
 
 from mypy.argmap import map_actuals_to_formals
 from mypy.nodes import ARG_POS, ARG_STAR, ARG_STAR2, ArgKind