Make `_C` extension a thin C wrapper (#39375)
Summary:
It just depends on a single `torch_python` library.
C library does not depend on standard C++ library and as result it closes https://github.com/pytorch/pytorch/issues/36941
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39375
Reviewed By: orionr
Differential Revision: D21840645
Pulled By: malfet
fbshipit-source-id: 777c189feee9d6fc686816d92cb9f109b8aac7ca
