Create script for updating submodules
Create script for updating submodules

We have to update LLVM, MLIR, and TF modules all the time and this should make it slightly less painful. It's got some checks in there and also doesn't do the actual push, so should also be reasonably safe.

Closes #183

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/iree/pull/183 from google:submodule 21cc64684242497fa5ee5878678d1b5af86b6244
PiperOrigin-RevId: 284873268

iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,google/iree,iree-org/iree,google/iree,google/iree,iree-org/iree