Add GCB config for fluentd-gcp build

[rvkubiak]

Adds a Google Container Builder config to build the fluentd-gcp image.
This will be used for build automation of Kubernetes addon images.

[x13n]

I think fluentd-gcp-image going away in favor of stackdriver-logging-agent. cc @crassirostris @bmoyles0117

[rvkubiak]

@tallclair Tim, do we want to remove fluentd-gcp-image from the list of core addons?

[rvkubiak]

As long as the images are in the addons directory included in the Kubernetes release, on any supported release branch (1.7, 1.8, 1.9), then we need to support them (and fix vulnerabilities). There might be a transition period where it's not worth the effort to automate some images that are going away.

Even if this image is being replaced in the future, we still want to automate the builds for current and previously supported releases.

[x13n]

Ack, makes sense. Can you also add some doc/information on how this config will be used?

FWIW, the PR to replace this image is already in flight: kubernetes/kubernetes#59128

There are other addons in this repository, are you going to add GCB configs for them as well?

[rvkubiak]

Sure, I can add some comments in the config. We identified 30 "core" addons (included in the Kubernetes manifest) to start working with an attempt at build automation. The primary goals of this are to decrease the number of humans with push access to k8s.gcr.io and to establish build provenance for these core addons.

The first set of 30 are more or less a proof of concept. The final plan for how these will be implemented isn't complete yet. Today these images are not regularly rebuilt, and we're aiming to use these configs to drive automated rebuilds based on criteria that aren't yet defined. One idea is to automatically rebuild and deploy when tags are pushed, but we need to get the community (specifically add-on owners) on board with a process.

We're using the first 30 as a proof of concept, and we're going to be seeking involvement from the community to determine what the final implementation will look like and help create the rest of the configs.

Other images from GoogleCloudPlatform that were identified as part of these 30 are event-exporter, kubelet-to-gcm, and prometheus-to-sd.

[rvkubiak]

Moving these configs to their own repo.