LV2=0 should always be passed in ardour's ebuild as per: http://ardour.org/node/4301#comment-25145 http://www.archlinux.org/news/ardour-loses-lv2-support/
The problem should be visible once liblrdf is patched for raptor2 API wrt bug 375025.
http://projects.archlinux.org/svntogit/packages.git/tree/ardour/trunk/raptor2.patch Maybe this will work and we can keep LV2 support. Needs liblrdf ported first.
Fixed by -r20