GitLab

Summary:
Extract the helper functions for defining library and extension so that they can be reused for building flashlight library and binding in https://github.com/pytorch/audio/issues/2580.

Pull Request resolved: https://github.com/pytorch/audio/pull/2585

Reviewed By: carolineechen

Differential Revision: D38233407

Pulled By: mthrok

fbshipit-source-id: 96f7c62a8b70bb3ff5caede9730165d54a55272f