CMake: Add optional precompiled header support (#61940)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61940
This adds a `USE_PRECOMPILED_HEADERS` option to the CMake build which
precompiles `ATen.h` and also `CUDAContext.h` for the cuda library.
After making a change in `native_functions.yaml`, this speeds up compilation
time by around 15% on my machine.
Test Plan: Imported from OSS
Reviewed By: heitorschueroff
Differential Revision: D29988775
Pulled By: malfet
fbshipit-source-id: a23c468c958a8b74ebaef052a5b2e5fa3836c64b
