Probably gentoo-sources maintainers will notice this anyway but just to make sure:
there's a patch in kernel git that didn't make it into 188.8.131.52, but is needed for building kernel with gcc 4.3.0. It's in the above url.
I hope it will go into next gentoo-sources release.
Fixed in gentoo-sources-2.6.24-r4 (genpatches-2.6.24-5), thanks for letting us know