Set LIVE_PASSES manually and install ubuntu-image.

live-build/auto/build

@@ -156,6 +156,11 @@ if [ "${IMAGEFORMAT:-}" = "ubuntu-image" ]; then
 fi
 
 if [ "$PROJECT" = "ubuntu-core-desktop" ]; then
+	export SNAPPY_STORE_NO_CDN=1
+	LB_UBUNTU_IMAGE_CHANNEL="${LB_UBUNTU_IMAGE_CHANNEL:-edge}"
+	snap install \
+            --classic --channel="$LB_UBUNTU_IMAGE_CHANNEL" ubuntu-image
+
 	# Special case for ubuntu-core-desktop - we need to call
 	# ubuntu-image twice, once for the core image payload and
 	# then for the actual image.

live-build/auto/config

@@ -833,6 +833,10 @@ case $PROJECT in
 		  size: @SIZE@
 		  variant: core 
 		EOF
+
+		# we have to manually mark the live layer as the LIVE_PASS, since it's also
+		# the only layer we build
+		LIVE_PASSES="live"
 		;;
 
 	ubuntu-oem)