dev-libs/boehm-gc and dev-libs/libgc refer to the same library. libgc only has version 6.6 while the other has versions 6.3 -- 6.7. The libgc ebuild should be removed.
no idea why this is assigned to me
(In reply to comment #1) > no idea why this is assigned to me # ChangeLog for dev-libs/libgc # Copyright 1999-2005 Gentoo Foundation; Distributed under the GPL v2 # $Header: /var/cvsroot/gentoo-x86/dev-libs/libgc/ChangeLog,v 1.1 2005/12/03 00:37:52 vapier Exp $ *libgc-6.6 (02 Dec 2005) 02 Dec 2005; Mike Frysinger <vapier@gentoo.org> : Initial import. Ebuild submitted by Ian Bygrave #35767 by Adam Hewgill.
looks like a good reason then libgc punted