Updating bazelbuild/platforms

Step 1: Make the release

• Pick a new version number

• run distro/make_rel.sh version

• Go to the Releases page

• Draft a new release

  • Name the release with a version number
  • Use the version number as the title
  • Copy the description that make_rel.sh produced to the description field.
  • upload the generated tar file

• use https://github.com/bazelbuild/continuous-integration/blob/master/mirror/mirror.sh to mirror the file

Step 2: Update Bazel