With commit 381b164559 media-tv/xbmc-9999 fails to configure without >=media-libs/taglib-1.8. This version of TagLib was released on 2012/09/05 and isn't in the tree. checking for TAGLIB... no configure: error: Could not find a required library. Please see the README for your platform.
should be all set now in the tree; thanks for the report! Commit message: Depend on taglib-1.8 to match upstream http://sources.gentoo.org/media-tv/xbmc/xbmc-9999.ebuild?r1=1.117&r2=1.118