Refactor build process for osbuilder and osbuilder-tools images

[jbalonso]

TL;DR:

I propose:

• [ ] merging the build processes for osbuilder and osbuilder-tools into a single repository
• using an Earthfile instead of a combination Makefile and Dockerfile

Justification

Support for osbuilder on arm64 is incomplete but appears unnecessarily difficult to advance.

In debugging issues around using osbuilder on my hybrid amd64/arm64 homelab, I found #451 (showing a the arm64 component of a multiarch image contained an amd64 binary), but I could not find the source material for the culprit osbuilder-tools image itself to contribute a fix. Moreover, I found kairos-io/helm-charts#5 because I needed to pin the manager to amd64 with a nodeSelector, but the presence of an arm64 manifest for osbuilder-tools shows that multiarch support was at least intended.

[jbalonso]

I found the osbuilder-tools image build process buried in an actions workflow and the tools-image/ directory.

[mudler]

Totally agree here - the Makefile is there because it is automatically generated by operator-sdk, indeed in other controllers you might find a Makefile and an Earthfile as well. We need to consolidate Earthfiles across all controllers too, as would help also much into testing too. feel to create an issue? 🙂