Created attachment 7289 Replace libxfce4ui-1 by libxfce4ui-2 in .pc file In configure script, xfce4-session needs libxfce4ui-2 but in libxfsm/xfce4-session-2.0.pc libxfce4ui-1 is still used. I think it's a typo, it should be libxfce4ui-2 (because xfce4-session has been ported to Gtk3). Patch fixes this issue.
Thanks Olivier, pushed to master in https://git.xfce.org/xfce/xfce4-session/commit/?id=e3c67a136486672a4db594564de2be992b20eca4