Build Multi-Arch Images 📦

[timuthy]

What this PR does / why we need it:
This PR lets the CI pipeline build multi-arch images with support for linux/amd64 and linux/arm64.

/kind enhancement
/area delivery

Which issue(s) this PR fixes:
Fixes parts of gardener/gardener#6258

Special notes for your reviewer:
The build steps have been unified along the way, i.e. make build builds the MCM binary locally for the system the build is executed on and make docker-image builds the MCM binary within the docker image. There is no dedicated local linux/amd64 build anymore as I didn't see any benefit of keeping it. Please let me know if you think otherwise.

Release note:

Published docker images for Machine-Controller-Manager are now multi-arch ready. They support `linux/amd64` and `linux/arm64`.

[himanshu-kun]

thanks for the PR
You would be raising similar PRs for the mcm-providers also right?
and would similar change be required in cluster autoscaler as i see the make build is capable of creating mulit-arch images (pls correct me if I am wrong) , but in the pipeline we create the binary like this which I think would not create multi-arch binary

[timuthy]

You would be raising similar PRs for the mcm-providers also right?

The primary goal of gardener/gardener#6258 is to have ARM support for the local dev environment. We can file PRs for MCM providers after supporting the local use case as testing this will involve more effort.

and would similar change be required in cluster autoscaler

Yes, I can file a PR for that.

[himanshu-kun]

You would be raising similar PRs for the mcm-providers also right?

The primary goal of gardener/gardener#6258 is to have ARM support for the local dev environment. We can file PRs for MCM providers after supporting the local use case as testing this will involve more effort.

and would similar change be required in cluster autoscaler

Yes, I can file a PR for that.

Thanks that would be great!

[himanshu-kun]

/lgtm