x11-themes/adwaita-icon-theme = x11-themes/gnome-icon-theme + x11-themes/gnome-icon-theme-symbolic, so...
This is going to be annoying to chase down as some packages have a configure check for it while it should never have been their role to check for that. If you can build a list of packages to fix, that would help.
Do we even need to check for any theme in evince ebuild now that gtk+ is pulling the adwaita-icon-theme set?
I see that evince 3.18.2 has at least dropped the unconditional dependency on gnome-icon-theme-symbolic. Is that enough to close this one?
yep