Support multi-arch builds
Related #2
Make the Dockerfile multi-architecture (aka multi-arch) by using some build arguments.
Once I find a way of attaching securely a runner supporting ARM, it should build an ARM image as well. So this is the first step in supporting other architecture than x86_64, but as long as I have access to only running with such architecture, I won't have readily "pull-able" images for ARM.
Edited by username-removed-463787