[feature request] Skip git call in setup.py if submodules are there

[crcrpar]

It seems like we call git submodule update --init --recursive even when we update submodules beforehand as per https://github.com/pytorch/text/blob/60bea668f7bf4359a447487555b9209ae5b1e07b/setup.py#L48-L57

Would you mind if you share your take on following what torchdata does here: https://github.com/pytorch/data/blob/901b48312179865657b90792aa03f0775ec50971/setup.py#L44?