While doing depends builds, I noticed that there are many configure flags that weren't recognized by our packages. This leads to things like: #16183. This is most likely caused by either overzealous configure flag adding, or updating depends packages without looking at changes to accepted configure flags.

I propose that we:

1. Prune configure flags from depends that packages don't understand.
2. Add documentation on updating packages (namely that new configure flags should be checked).
3. (stretch-goal) Find out what --without- and --disable- configure flags we can supply to speed up depends builds.

CC @fanquake @theuni