We need to double-check how/where XDG_RUNTIME_DIR is set.

There are at least 2 right now: /run/user/0 vs. /run/user/root

agl-master/build$ repo grep XDG_RUNTIME_DIR | cat
meta-agl/meta-agl-bsp/meta-raspberrypi/recipes-graphics/wayland/weston/weston.sh:if test -z "$XDG_RUNTIME_DIR"; then
meta-agl/meta-agl-bsp/meta-raspberrypi/recipes-graphics/wayland/weston/weston.sh: export XDG_RUNTIME_DIR=/var/run/user/root
meta-agl/meta-agl-bsp/meta-raspberrypi/recipes-graphics/wayland/weston/weston.sh: mkdir --parents $XDG_RUNTIME_DIR
meta-agl/meta-agl-bsp/meta-raspberrypi/recipes-graphics/wayland/weston/weston.sh: chmod 0700 $XDG_RUNTIME_DIR
meta-agl-extra/meta-app-framework/recipes-example/afb-client/files/afb-client:if [ -z "${XDG_RUNTIME_DIR+1}" ]; then
meta-agl-extra/meta-app-framework/recipes-example/afb-client/files/afb-client: export XDG_RUNTIME_DIR=/run/user/$UID
meta-agl-extra/meta-app-framework/recipes-example/afm-client/files/afm-client:if [ -z "${XDG_RUNTIME_DIR+1}" ]; then
meta-agl-extra/meta-app-framework/recipes-example/afm-client/files/afm-client: export XDG_RUNTIME_DIR=/run/user/$UID
poky/documentation/ref-manual/technical-details.xml: <filename>XDG_RUNTIME_DIR</filename>:
poky/documentation/ref-manual/technical-details.xml: export XDG_RUNTIME_DIR=/tmp/$USER-weston
poky/meta/recipes-graphics/wayland/weston-init/init: if test -z "$XDG_RUNTIME_DIR"; then
poky/meta/recipes-graphics/wayland/weston-init/init: export XDG_RUNTIME_DIR=/run/user/root
poky/meta/recipes-graphics/wayland/weston-init/init: mkdir --parents $XDG_RUNTIME_DIR
poky/meta/recipes-graphics/wayland/weston-init/init: chmod 0700 $XDG_RUNTIME_DIR
poky/meta/recipes-graphics/wayland/weston-init/weston.service:Environment="XDG_RUNTIME_DIR=/run/user/root"
poky/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession.d/13xdgbasedirs.sh:# Wayland needs XDG_RUNTIME_DIR, so set it to /tmp. This isn't compliant with
poky/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession.d/13xdgbasedirs.sh: XDG_RUNTIME_DIR="/tmp"
poky/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession.d/13xdgbasedirs.sh: export XDG_RUNTIME_DIR