weston/profile: Adapt the XDG_RUNTIME_DIR to the weston user

weston is now started as user weston. This leads to a weston socket
in the users runtime dir. To make it possible to start UI tools as
root from the cmdline, this adapts the exported XDG_RUNTIME_DIR to
the new socket location.

recipes-core/base-files/base-files/profile_d_qtenv.sh

 # Defaults to allow start of gui tools from the commandline
-export XDG_RUNTIME_DIR=/var/run/user/0
+export XDG_RUNTIME_DIR=/var/run/user/1000
 export QT_QPA_FONTDIR=/usr/share/fonts/truetype
 export QT_QPA_PLATFORM=wayland