Created attachment 418278 [details] build.log If you set your Qt version to "5" in qtchooser and then try to merge media-gfx/graphviz with USE="qt4", it will fail to compile. During compilation it complains about wrong version of moc and terminates the process (see line 3754 of build.log). After setting QT_SELECT to "4", everything works as expected. I've encountered this issue because Qt 5 is chosen as default on my system. The same issue already happened several times with e.g. media-sound/clementine.
The ebuild should inherit qmake-utils and call $(qt4_get_bindir)/qmake instead.
Thanks, fixed in git. https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=21f168dbd2fcd361280f0312a536faf0c18ad3df