Remove tools/setup_helpers/cuda.py. (#28617)
Summary:
Except for the Windows default path, everything it does has been done in
FindCUDA.cmake. Search for nvcc in path has been added to FindCUDA.cmake (https://github.com/pytorch/pytorch/issues/29160). The Windows default path part is moved to
build_pytorch_libs.py. CUDA_HOME is kept for now because other parts of
the build system is still using it.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28617
Differential Revision: D18347814
Pulled By: ezyang
fbshipit-source-id: 22bb7eccc17b559ce3efc1ca964e3fbb270b5b0f
