Create container for building own Anbox images

The following discussion from !956 (merged) should be addressed:

I'd like to create our own Android image to use, but the effort to produce it with pure Alpine is not worth it.
Instead I suggest we write down the exact steps to produce such an image, and make a Docker/Podman/LXC container which automatically executes those and produces a working image. We can then upload it somewhere for anbox-image to use.
— @PureTryOut