Fix dll load logic for Python 3.8 on Windows (#32215)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/31181 and https://github.com/pytorch/pytorch/pull/31162#discussion_r362495611.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32215
Differential Revision: D19501869
Pulled By: ezyang
fbshipit-source-id: 363824e52d2592ad968ecf1df345aa4c0daff915
