Use your Mac as a GitLab Runner

Install GitLab Runner for Apple silicon, register it with the shell executor and run it as a service.

From GitLab’s macOS install guide, over SSH on your Mac:

sudo curl --output /usr/local/bin/gitlab-runner \
  "https://s3.dualstack.us-east-1.amazonaws.com/gitlab-runner-downloads/latest/binaries/gitlab-runner-darwin-arm64"
sudo chmod +x /usr/local/bin/gitlab-runner

Register it with your project or group (in GitLab: Settings → CI/CD → Runners → New project runner), and choose the shell executor, which GitLab recommends for iOS and macOS builds. Then install it as a service:

cd ~
gitlab-runner install
gitlab-runner start

GitLab Runner on macOS runs as a LaunchAgent: it works only while dev is logged in to the desktop. GitLab recommends turning on automatic login (System Settings → Users & Groups) so the runner comes back after a reboot.