Create FreeBSD / FreeNAS 12 OS branch
As apart of our shift to 12, we'll need to create a proper branch in freenas/os. We should probably start with "HEAD" as well, since there's no harm in rolling snapshots of HEAD periodically, but I'll leave that decision up to you either way.
As apart of this new branch, please create an IXNAS kernel config in sys/amd64/conf so we can use that on both FreeNAS & TrueNAS and ship identical kernels if possible.
Once done, let me know and we'll switch the repos around in the 12 build system, since it's currently pointed at trueos/trueos.