do the `check-meta` last instead of first

[amjoseph-nixpkgs]

Could we please have ofborg do the meta checks last rather than first? Or perhaps concurrently with the other checks.

Ofborg seems much slower lately.

All of ofborg's tasks are incremental except for the meta checks. But the meta checks always take the same amount of time no matter how large or small a change is. That means we should do them last instead of first.