Add linux-arm64 autobuild binaries

We require gitlab-ci-multi-runner-linux-arm64 in our setup, i.e., the linux-arm64 configuration, and it would be great if binaries for this os-architecture configuration could be provided, as it's currently not automatically build and provided at https://gitlab.com/wiget/gitlab-ci-multi-runner/blob/master/docs/install/bleeding-edge.md. Adding debian packages for this configuration would be even better.