Actually call unlink, and add more typing

cibuildwheel/windows.py

@@ -175,7 +175,7 @@ def setup_setuptools_cross_compile(
         )
         return
     else:
-        atexit.register(lambda: distutils_cfg.unlink)
+        atexit.register(lambda: distutils_cfg.unlink())
 
     # Ensure our additional import libraries are made available, and explicitly
     # set the platform name

test/test_testing.py

@@ -72,7 +72,7 @@ class TestSpam(TestCase):
 '''
 
 
-ADD_ENV = {}
+ADD_ENV: dict[str, str] = {}
 
 if utils.platform == "windows":
     if platform.machine() != "ARM64":