CMake: Fix python dependencies in codegen (#45275)
Summary:
I noticed while working on https://github.com/pytorch/pytorch/issues/45163 that edits to python files in the `tools/codegen/api/` directory wouldn't trigger rebuilds. This tells CMake about all of the dependencies, so rebuilds are triggered automatically.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45275
Reviewed By: zou3519
Differential Revision: D23922805
Pulled By: ezyang
fbshipit-source-id: 0fbf2b6a9b2346c31b9b0384e5ad5e0eb0f70e9b
