d/rules: Avoid letting inkscape try to connect to the session bus

In some build environments, this will fail with:

    terminate called after throwing an instance of 'Gio::DBus::Error'

resulting in a build failure. The environment variables used here
are borrowed from game-data-packager, which also calls inkscape
programmatically.

debian/rules

@@ -1,4 +1,17 @@
 #!/usr/bin/make -f
 
+# Turn off features of Inkscape and its dependencies that would normally
+# try to connect to the D-Bus session bus
+export DBUS_SESSION_BUS_ADDRESS=invalid:
+export GIO_USE_MEMORY_MONITOR=none
+export GIO_USE_NETWORK_MONITOR=netlink
+export GIO_USE_PORTALS=0
+export GIO_USE_POWER_PROFILE_MONITOR=none
+export GIO_USE_VFS=local
+export GIO_USE_VOLUME_MONITOR=unix
+export GSETTINGS_BACKEND=memory
+export GTK_USE_PORTAL=0
+unexport XDG_RUNTIME_DIR
+
 %:
 	dh $@