The freedesktop specification says that the autostart folder is located at $XDG_CONFIG_DIRS/autostart. Nixos defines XDG_CONFIG_DIRS as /etc/xdg. So we need to copy the desktop files into the right folder with make-startupitem.
See c556a6ea46.
c556a6ea46
svn path=/nixpkgs/trunk/; revision=32686
svn path=/nixpkgs/trunk/; revision=31958