hipify: do not overwrite files that stay the same (#23112)
Summary:
This is a small patch to not overwrite unchanged files to help a bit with building.
It is not as incremental as one might like, given that one has to pass `--out-of-place-only` to not run into the patching and things.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23112
Differential Revision: D16402623
Pulled By: bddppq
fbshipit-source-id: 531ce0078bc716ae31bd92c5248080ef02a065b9
