Upgrade bazel to 1.2.0. (#30885)
Summary:
Companion diff for https://github.com/pytorch/xla/pull/1464. Should land only after the pytorch/xla PR is in.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30885
Differential Revision: D18866835
Pulled By: ailzhang
fbshipit-source-id: 51f4d2770f8ef873a659579ddd81a42957ffb885
