gentoo-sources-2.4.22-r1 no longer includes systrace. This was included in earlier versions of gentoo-sources. Its not clear if the ommission is an oversight, an intentional choice to remove that package, lack of interest, or lack of working patch. I have been using the patch 40_selinux-systrace-v1.4-2.4.22.patch from hardened-sources-2.4.22 applied to gentoo-sources-2.4.22-r1. I does not apply completely cleanly - there is one small chunk that needs to be applied by hand. I am very happy with this so far.
This is now in -r5. Thanks Brian...