re: bsd make

[matthew green <mrg@eterna.com.au>]

   that get ported can Provide: (since something like 90%+ of packages don't
   need anything that isn't shared between all four variants I know of in
   common use), and stop trying to pretend they're mergeable into a single
   utility.

i'd expect macos & freebsd to converge on the same tool.  the rest
have incompatible changes that make it much harder to merge them in
any real sense.  mostly these are make modifier changes, but they're
significant in build native sources for each system...