allow building docker without torchvision (#26168)
Summary:
There is an issue with the torchvision version not matching the pytorch version if one builds the docker from a tag, see issue https://github.com/pytorch/pytorch/issues/25917. The current solution requires one to re-init the submodules or manually change the version of torchvision. This PR allows one to build the docker image without torchvision, which not only fixes the above mentioned bug but also frees non-image pytorch users from the tyranny of torchvision :laughing:.
In all seriousness, for NLP researchers especially torchvision isn't a necessity for pytorch and all non-essential items shouldn't be in the docker. This option removes one extra thing that can go wrong.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26168
Differential Revision: D17550001
Pulled By: soumith
fbshipit-source-id: 48b8b9e22b75eef3afb392c618742215d3920e9d
