[dateutil] Check platform before imports

Otherwise imports may fail on other platforms.

Author: eliroca

stubs/python-dateutil/dateutil/tz/win.pyi

@@ -1,13 +1,13 @@
 import sys
-from ctypes import _NameTypes, _Pointer, c_wchar
-from datetime import datetime, timedelta
-from typing import Any, ClassVar, Final
-
-from dateutil.tz import tzwin as tzwin, tzwinlocal as tzwinlocal
 
 if sys.platform == "win32":
+    from ctypes import _NameTypes, _Pointer, c_wchar
+    from datetime import datetime, timedelta
+    from typing import Any, ClassVar, Final
     from winreg import _KeyType
 
+    from dateutil.tz import tzwin as tzwin, tzwinlocal as tzwinlocal
+
     __all__ = ["tzwin", "tzwinlocal", "tzres"]
 
     ONEWEEK: timedelta