Backport enabling of adding extra snaps to ubuntu-core images via the EXTRA_SNAPS environment

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.408.56) UNRELEASED; urgency=medium
+
+  * Backport enabling of adding extra snaps to ubuntu-core images via the
+    EXTRA_SNAPS environment (LP: #1849491).
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Wed, 30 Oct 2019 17:28:57 +0100
+
 livecd-rootfs (2.408.55) xenial; urgency=medium
 
   * magic-proxy: dump proxy log to stdout on failure (LP: #1847300)

live-build/auto/config

@@ -180,6 +180,9 @@ case $IMAGEFORMAT in
 				MODEL="ubuntu-core-18-${MODEL#pc-}" ;;
 		esac
 
+		for snap in $EXTRA_SNAPS; do
+			UBUNTU_IMAGE_ARGS="$UBUNTU_IMAGE_ARGS --extra-snaps $snap"
+		done
 		echo "IMAGEFORMAT=$IMAGEFORMAT" >> config/common
 		echo "UBUNTU_IMAGE_ARGS=\"$UBUNTU_IMAGE_ARGS\"" >> config/common
 		# Store model assertion in top dir to get it picked up later as a build artifact