font-manager 0.9.4 fails to compile against gtk4 4.22: the
Gtk.DragIcon.get_for_drag binding changed in the gtk4 vapi, producing
'use new operator' errors in Collections.vala and FontList.vala that
broke home-manager-path for all desktop hosts.
0.9.4 is the latest upstream release (master unfixed too); the fix is
upstream PR FontManager/font-manager#468, already carried by nixpkgs
master but predating our locked nixpkgs and nixpkgs-master inputs.
Vendor the patch as an overlay mod, following the aardvark-dns pattern.
Drop once the nixpkgs lock carries it.
