Experimental Linux/FreeBSD/OpenBSD/OSX11 release : http://dl.free.fr/oLYL88VWq

Not official. Only for testing.

This is what I was working on.
It's not so complex and it should work on every POSIX OS. At least on Linux, FreeBSD and OpenBSD.
It also support rpm distribution (with 'rpmbuild -tb upp-14352MS.tar.xz')

(Patch for OpenBSD Package Organizer configs included).

I stop there because I think Mirek wants something simpler, smaller and easier to maintain.
At least, you can use the buildrequires.posix file to enhance the current posix release tarball.