As Martin notes, my concern is that I can go for years without having to touch the low level files (since syntax changes are rare), so it's important to me to make it easy to remember and/or relearn how to regenerate them.

However, suitable make commands (e.g. a "make regen" target, with "make regen-X" subtargets) would qualify as "easy to remember", and would also be amenable to automated testing in combination with a `make clobber-gen` command.

(Tangent on target naming: I think 'rebuild' would be confusing, while 'regenerate' is a bit long, especially if there are more specific subtargets. 'regen' is just a shortened version of the latter)