Refactor macOS build and test (#25930)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25930
This commit temporarily enables the following builds for this PR:
* pytorch_macos_10_13_py3_build
* pytorch_macos_10_13_py3_test
[test macos]
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25930
Test Plan: Imported from OSS
Differential Revision: D17318583
Pulled By: pietern
fbshipit-source-id: d12f04b148318711e8a15def7dca12b8d7ef65d3
