Build staging images for KMM

[qbarrand]

Kubernetes guide: https://github.com/kubernetes/k8s.io/tree/main/k8s.gcr.io#creating-staging-repos

• Create the staging repo for KMM images
• Enable automatic builds

[qbarrand]

PR for the CloudBuild config: #56
PR for the postsubmit job: kubernetes/test-infra#27461

[ybettan]

I think that if you write Fixes <issue link> on a PR (comment or description) it will autoclose the issue when the PR is merged.
FYI @qbarrand

[qbarrand]

Slack thread for the bucket creation: https://kubernetes.slack.com/archives/CCK68P2Q2/p1663659562229129

[qbarrand]

Bucket creation is now complete ✅
Builds are still failing because Prow clones the git repo without the .git directory: https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/post-kernel-module-management-push-images/1572475993145217024#1:build-log.txt%3A88-89
Opened a Slack thread in #sig-testing.

[qbarrand]

More work needed to include the .git directory in build sources:

• Ignore the default .gcloudignore rule for .git: Include .git in image builds #92
• Add a command-line flag in the postsubmit job: Upload the .git directory to GCB for KMM builds kubernetes/test-infra#27650

[qbarrand]

Operator builds are now running after each commit to main.

• postsubmit job
• Google Cloud console
• Google Cloud Builds config

Closing this issue.