Adds a kube::release::gcs::publish_latest_official that checks the
current contents of this file in GCS, verifies that we're pushing a
newer build, and updates it if so. (i.e. it handles the case of
pushing a 0.13.1 and then later pushing a 0.12.3.) This follows the
pattern of the ci/ build, which Jenkins just updates unconditionally.
I already updated the file for 0.13.1. After this we can update the
get-k8s script, so we don't have to keep updating it.
* Rewrite a bunch of the hack/ directory with modular reusable bash libraries.
* Have 'build/*' build on 'hack/*'. The stuff in build now just runs hack/* in a docker container.
* Use a docker data container to enable faster incremental builds.
* Standardize output to _output/{local,dockerized}/bin/OS/ARCH/*. This regularized placement makes cross compilation work.
* Move travis specific scripts under hack/travis
With new dockerized incremental builds, I can do a no-op `make quick-release` in ~30s. This is a significant improvement.
