allow user passing relative paths in include_dirs within setuptools.setup (#38264)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/38264
Test Plan: Imported from OSS
Differential Revision: D21509277
Pulled By: glaringlee
fbshipit-source-id: b0bc17d375a89b96b1bdacde5987b4f4baa9468e
