There is a ebuild for gnome-globalmenu 0.7.4. I am new to ebuilds writing so it is possible that there should be some improvements but this ebuild works and I've got gnome-globalmenu working on my Gentoo Linux.
Created attachment 185388 [details] gnome-globalmenu-0.7.4.ebuild ebuild for 0.7.4 version.
*** This bug has been marked as a duplicate of bug 205203 ***