Make arch-specific releases use separate images instead of tags on the same image

[towca]

This seems to be the current convention in k8s.

[towca]

@hakman, you introduced arch-specific builds to the Makefile. Could you please take a look?
/assign @hakman

[hakman]

@towca In general this is true, but not sure if there is support support for pushing manifests using cross repo references. If you really want the -amd64 and -arm64 images pushed to the corresponding repos, may be safer to retag with the corresponding suffixed images.

If you look at what is actually pushed to the prod repo from staging, you will see that there are no tags for the -amd64 and -arm64 images, just the main one, so cleanup is done by the promoter.
https://console.cloud.google.com/gcr/images/k8s-artifacts-prod/EU/autoscaling/cluster-autoscaler

[towca]

The process of promoting images from staging to prod is completely manual. We haven't promoted any arch-specific cluster-autoscaler images yet. I want to promote an arm64 image right now, hence the changes. The promotion shouldn't be an issue, the same thing has already been done for Vertical Pod Autoscaler: kubernetes/k8s.io#1318.

[hakman]

Simplified things a bit. My concern was that the push to staging won't work.
Also, if you want to push the ARM64 image in kubernetes/k8s.io#1485, you should also push the AMD64 one.

[towca]

I've already tested pushing to staging, so that shouldn't be a concern (gcr.io/k8s-staging-autoscaling/cluster-autoscaler-arm64:v1.20.0).

I'm building and promoting the arm64 image for a previous release specifically because somebody asked for it during the SIG meeting. All next releases will have all 3 images released. But sure, I can include the amd64 image as well.

[hakman]

Thanks. I tested this also and worked fine for me.
/lgtm

[towca]

Thanks for the review!
/assign @MaciekPytel

[hakman]

Thanks for the releases @towca :)

[mwielgus]

/lgtm
/approve

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