Update Bazel Docker container for new release

To build and publish docker container for new Bazel LTS release to gcr.io/bazel-public/bazel, follow those steps: (The build.sh file can be found here.)

1. Build the docker container on your local Linux machine

$ ./build.sh gcr.io/bazel-public/bazel <bazel version>

2. Push the docker container to gcr.io/bazel-public/bazel

$ docker push gcr.io/bazel-public/bazel:<bazel version>

3. Update the latest tag if necessary

If the new Bazel version is the latest version (not a minor/patch release for previous major LTS version):

$ docker image list gcr.io/bazel-public/bazel:<bazel version>   # To check the <IMAGE ID>.
$ docker tag <IMAGE ID> gcr.io/bazel-public/bazel:latest
$ docker push gcr.io/bazel-public/bazel:latest