The last stable geos version on portage (3.3.3) isn't compatible with ruby19, so it fails if I eselect ruby19 as default.
Portage already has geos versions 3.3.4 and 3.3.5, but only the last one is compatible with both ruby18 and ruby19. Since ruby19 will be the default implementation on gentoo , geos-3.3.5 should be unmasked.
Almost two months gone by - I can't find any bug related to 3.3.5.
Meanwhile, geos-3.3.6 is out: http://trac.osgeo.org/geos/browser/tags/3.3.6/NEWS
Update - geos-3.3.7 is out and solves bug 450998, also I found out about it building just fine against current stable php-5.4.8 in bug 455118.
We'll shoot for a 3.3.8 stabilization.
Bug 450998 was not fixed, but will be shortly. Same with 455118.
x86 stable. Last arch, closing...