Tested on both 13.0-RELEASE and 14.0-CURRENT:
- `mac_sched` kernel module builds and loads
- Members of the `realtime` group **can** run processes at realtime priority
- Non-members of the `realtime` group can **not** do that
- Enable / disable functionality through `sysctl security.mac.sched.realtime`
- Change of group id through `sysctl security.mac.sched.realtime_gid` is effective