Publish images for the linux/arm64 Docker platform

[ianks]

In #76 I mentioned a request to publish linux/arm64 Docker images. Currently, building on M1 is unbearably slow in many cases due to the virtualization overhead. I’ve almost given up on running RCD locally as a result.

Using linux/arm64 images removes the virtualization overhead and makes the local development experience much better.

[flavorjones]

@ianks I'm curious - is the aarch64-linux support not sufficient for your needs?

[ianks]

@ianks I'm curious - is the aarch64-linux support not sufficient for your needs?

I'm referring to the issue of compiling x86_64-linux on an arm64 machine. Currently, that requires full CPU emulation. Ideally, RCD could cut the x86_64-linux, etc images for multiple Docker platforms (linux/arm64 and linux/amd64)

[flavorjones]

Ah, right, I had totally forgotten the original context of this issue. Thanks for re-explaining.

[ianks]

@flavorjones I think this issue becomes simple to tackle now with Ubuntu base images

[flavorjones]

@ianks If you have the bandwidth, I'd gladly accept help. I'm unlikely to get to this in the next few weeks.

[ianks]

Been working on adding support to the cross-rs images, since they have all the bells and whistles already and already inherit from ubuntu:20.04. Once I get that merged, it should be a one line change here (and likely able to remove a bunch of code)

cross-rs/cross#1597