So this is pretty misleading. It's really a full system emulator (qemu) running inside Docker, using root privileges on the container that make the isolation very weak (--privileged). It also uses hardware assisted virtualization (KVM) which is not going to be available most of the time Docker is. You can think of the Docker platform itself as subset of the Linux platform. With many common features removed by default…
I don't care though. What I care about is that it's a pain in the butt to do CI/CD pipelines for an application with iOS/OSX support. So if someone has a headless OS X contraption on offer, I want to hear some more about it. The last time I set this up, a manager decided he wanted a laptop like the rest of us instead of the iMac he got. He asked semi-jokingly if someone wanted the machine for anything and I said "Yes…
Still, very interesting idea!