Followup to D60925, this time, for checker options. Non-checker configurations should receive the same treatment eventually.
The patch is marked WIP, because I am not really confident about osx checkers, and I can see valid uses for the rest of the options, but I might not be strict enough on this. Also, @NoQ suggested that hidden checker's options should be hidden by default, but I'm kind of hesitant about it, as described in D57858#1499414.
Also, the TableGen code is very ugly, I might want to have another attempt at making it nicer.