Set shell options for reliability.

Tweak a few other small things in our shell scripts.
Confirm pull of golang:cross as it is huge (1.8G)
Option in `build/release.sh` to skip tests for a quicker dev/test cycle.
Add a `release` target to `Makefile`

The rest of the reconciliation with new `build` methods will come later.
Apply SELinux policy to _output dir so "build in docker" works on RHEL.
Uniquify docker names

If you have two repos that are both building at the same time we don't want to have them stomp on each other as they deal with docker.  Work around this by hashing the KUBE_ROOT and mixing that in to the name.