GitLab

Summary:
At the time of release, we need to download doc built by CI.
CircleCI does not have feature to download multiple files.

This commit add the archive of built documentations as
CI artifact so that the whole documentation can be downloaded
at once.

Resolves https://github.com/pytorch/audio/issues/2340

Pull Request resolved: https://github.com/pytorch/audio/pull/2448

Reviewed By: hwangjeff

Differential Revision: D36942077

Pulled By: mthrok

fbshipit-source-id: 61dde0d71841434a3d0624404d99911aa6956f88