Ubuntu 14.04 is about to be end-of-life and Bazel CI will stop supporting it shortly afterwards. Context: https://groups.google.com/d/msg/bazel-dev/_D6XzfNkQQE/8TNKiNmsCAAJ
This was previously present in https://github.com/bazelbuild/continuous-integration, but the Bazel team asked us to move it to our repo. It will be helpful if we need to change the build configuration, eg to add new platforms.