Comment 0 for bug 1964615

Starting yesterday we started seeing failures in focal builds in a PPA:

https://launchpad.net/~mir-team/+archive/ubuntu/dev/+build/23237481

I tracked it down to `XDG_RUNTIME_DIR` being set to `/run/user/$UID` all of a sudden. Some other variables also got set:

 APT_CONFIG=/var/lib/sbuild/apt.conf
+DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/2001/bus
 DEB_BUILD_OPTIONS=parallel=4
 HOME=/sbuild-nonexistent
 LANG=C.UTF-8
@@ -20,3 +21,7 @@
 TERM=unknown
 USER=buildd
 V=1
+XDG_RUNTIME_DIR=/run/user/2001
+XDG_SESSION_CLASS=background
+XDG_SESSION_ID=c81
+XDG_SESSION_TYPE=unspecified