Install cpp tests when built (#15000)
Summary:
This is broken out of https://github.com/pytorch/pytorch/pull/13733/
We want to install cpp tests so they can ultimately be runnable from that location for Caffe2 tests run from PyTorch builds.
cc pjh5 yf225 anderspapitto
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15000
Reviewed By: pjh5
Differential Revision: D13416253
Pulled By: orionr
fbshipit-source-id: 51280be0a22557a742f90c9f303c58c35cbd4a38
