Implement a hacky workaround to support pushing images from Jenkins

[ixdy]

I attempted to use #355 in the cross-build job, but it failed for two reasons:

• the version of docker on Jenkins is old enough (1.9.1) that it doesn't embed manifest.json in saved docker images.
• Jenkins doesn't have jq installed

Fixing this on Jenkins is a nontrivial process; until we do that, there are hacky workarounds.

x-ref kubernetes/test-infra#1400

/assign @david-mcmahon
cc @luxas @madhusudancs @roberthbailey

[david-mcmahon]

Well that's sufficiently gross. :) Not having access to jq is going to be a big hindrance to getting anago running generally via jenkins as well. I guess there's nowhere else that need jq from jenkins? Is there a more general solution for jq-less environments here?

[ixdy]

We probably should just install jq on the Jenkins VMs, though I'm not sure how involved of a process that will be.

[david-mcmahon]

/lgtm

[ixdy]

I think I'm going to focus on kubernetes/test-infra#3274 instead.

[roberthbailey]

Shall we close this PR then?

[david-mcmahon]

I did lgtm this, but I'm also quite happy to have jq on the jenkins images. And by gross, of course I meant awesome regex-slingin' (which I do appreciate!). Thanks for doing this.

[ixdy]

getting everything to run inside a container so it's isolated from the environment of Jenkins (or prow) is still the ideal end goal, of course.

(I briefly considered either putting push-build.sh inside a container, or using one of the jq docker images. Not sure whether that's better or worse than installing jq on the Jenkins VMs.)