Support Buildkit drivers for image builds

[pl4nty]

Buildkit drivers offer a lot of additional features over the default docker driver, like multi-arch images and remote builders.

They could be supported by moving tag/push to docker build --push, depending on docker buildx which became the default for docker engine in Feb 2023. Buildx/buildkit has other benefits too eg native caching for CI environments, that would be useful to support in a future PR.

Happy to send a PR for this if you want.