It an entry under window decorations and icons, but not under "style". It seemed to compile properly otherwise.
Hanno: please take a look at this (since you're the redhat-artwork-guy ;)
Apparently the .so and .la are copied to the wrong dir, see this thread for info: http://forums.gentoo.org/viewtopic.php?t=30003
Should be fixed, please let us know if it still doesn't work for you.