As per summary. See blocked tracker bug for more information. P.S. As per QA team decision you are free to leave USE="multislot" in eclass, but not in in-tree ebuilds of sys-devel/gcc. Some trickery is needed to achieve that - it's up to you.
Maintainer timeout, USE flag is masked in base profile
*** This bug has been marked as a duplicate of bug 174407 ***