Use setuptools for build_ext as well

Author: ilevkivskyi

mypyc/lib-rt/setup.py

@@ -9,10 +9,10 @@
 import subprocess
 import sys
 from distutils import ccompiler, sysconfig
-from distutils.command.build_ext import build_ext
 from typing import Any
 
 from setuptools import Extension, setup
+from setuptools.command.build_ext import build_ext
 
 C_APIS_TO_TEST = [
     "init.c",