Build system stuff

This is some things mostly noticed during my investigation of the dev/tests branch as well as !27 (merged). Some of it is slightly cosmetic (removed one build option that was doing nothing and wasn't expected to do anything later) or "cleanliness" (moving some stuff to find modules), though it's mostly "this was buggy for me" or "this might be buggy for someone".

Doesn't address the range of other "build options" that don't actually control anything at the moment, since that became a big rabbit hole once I poked it. I'll file issues to request insight.