torchvision doesn't recompile if torchvision/csrc/ROIAlign.h is edited

[ezyang]

Steps to reproduce:

1. Build torchvision python setup.py develop
2. Introduce error to torchvision/csrc/ROIAlign.h
3. Rebuild

[ezyang]

I verified that ninja is tracking header dependencies correctly; what seems to be happening is setup.py is bypassing calling ninja entirely

[ezyang]

I guess this is the same root cause as what caused us to change how PyTorch setup works: pytorch/pytorch#16162

[ezyang]

cc @zou3519

[ezyang]

Fix is in pytorch/pytorch#40837