Enable qemu-user-static binfmt-misc on gitlab CI runners
Cross compiling is really simple with docker images and installing whatever toolchains you want. But cross-execution with qemu is a lot more pain. You can run binaries in docker images using qemu-user, but that means build system changes, since every time you run a binary you need to wrap it. Which is a pain, if your unit tests aren't directly binaries, but scripts that wrap binaries, and then maybe exec() other binaries.
Much simpler if you can set up binfmt-misc support, which means any non-native binaries get executed as if they're native. Unfortunately binfmt-misc isn't namespaced, so can't be set up from within a docker image. Note that there's some tricks to make sure it all keeps working within mount namespaces, but qemu-user-static should take care of that for you.