Automatically set BUILD_SPLIT_CUDA for cpp exts (#52503)
Summary:
Fixes https://github.com/pytorch/vision/pull/3418#issuecomment-781673110
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52503
Reviewed By: malfet
Differential Revision: D26546857
Pulled By: janeyx99
fbshipit-source-id: a100b408e7cd28695145a1dda7f2fa081bb7f21f
