solution to depend on cached set of variable values

[Britton Kerin]

I've got vars like DEBUG_ENABLE only a big hairy pile of them at this
point, and I want make to rebuild everything when I give a different
set of them (including via command line) with my having
to remember to do clean first.

I can see how it might be done using .VARIABLES and a cache of some
sort but I wonder if anyone has already done this?

Britton