You appear to be right, but I don't know anything about it.
That's exciting, though - it would be really cool if Makefiles could do more computation. Maybe then we'd get an easier-to-use autoconfiguration system!
On one hand I'm a bit afraid that this might add more complexity to an already complex tool. But on the other hand the current tools in Make are very ugly to use. So Guile could certainly be an improvement.
edit: http://lists.gnu.org/archive/html/guile-user/2012-01/msg0006...