Add ability to query if built with CUDA and MKL-DNN. (#18362)

Add ability to query if built with CUDA and MKL-DNN. (#18362)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18362
ghimport-source-id: 374b7ab97e2d6a894368007133201f510539296f

Stack from [ghstack](https://github.com/ezyang/ghstack):
* #18242 Test running a CUDA build on CPU machine.
* **#18362 Add ability to query if built with CUDA and MKL-DNN.**

Fixes #18108.

Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Differential Revision: D14584430

fbshipit-source-id: 7605a1ac4e8f2a7c70d52e5a43ad7f03f0457473