add arm64 builds to docker hub

[lockbox]

This PR adds the necessary fixes to make the arm64 builds work for fw2tar. This change was all that was required to make the docker build succeed, but I still have the question of "what is the proper way to add arm64 image builds to CI?" since right now the actions are all ran on rehosting-arc.

There are a few options, I think the least work for you guys would be one of these two options:

• add a new CI yaml that performs the publish.yaml jobs logic without the rehosting-arc specific stuff
• add a matrix to the CI yaml's, and conditionally perform the rehosting-arc specific logic if the runs-on: matrix target is rehosting-arc

Would either of the above be something you are open to? My only real end goal here is to get arm64 docker images of fw2tar pushed to dockerhub. In-house I'm building them fine but I don't want to have to continue to maintain different logic for fw2tar if I don't have to.

LMK and I can add the proper changeset!