Report CUDA separate compilation flag (#35726)
Summary:
In Summary specify whether CUDA code is compiled with separate compilation enabled
Also, correctly handle space-separate TORCH_NVCC_FLAGS when adding them to NVCC_CUDA_FLAGS
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35726
Test Plan: CI + local build with TORCH_NVCC_FLAGS set to "-Xfatbin -compress-all"
Differential Revision: D20830885
Pulled By: malfet
fbshipit-source-id: 0e0ecab4a97b6c8662a2c4bfc817857da9f32201
