Test running a CUDA build on CPU machine. (#18242)

Test running a CUDA build on CPU machine. (#18242)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18242
ghimport-source-id: b949d312a48226a34f90304162e910acee7c95cd

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.

Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Differential Revision: D14584429

fbshipit-source-id: b54de5b33f0c795a7d9605d30576cdf9b74050fd