cirrus-ci.com also has the possibility to run CI tasks on macOS.
Since most of the QEMU developers do not have access to macOS yet,
let's add a CI pipeline for this operating system here, too.
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: NEd Maste <emaste@freebsd.org>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>