variable squashfs compression level

Makefile

@@ -6,6 +6,8 @@ DOCKER_IMAGE ?= labsync-builder
 
 CWD=$(abspath $(patsubst %/,%,$(dir $(abspath $(lastword $(MAKEFILE_LIST))))))
 
+COMPRESSION_LEVEL ?= 5
+
 qemu_ifname_br = brlabsync
 qemu_ifname_tap = taplabsync
 qemu_hostname = qemumachine
@@ -52,6 +54,7 @@ images/debian-stretch.squashfs: images
 		-e "group=`id -g`" \
 		-e "ANNOUNCE=$(ANNOUNCE)" \
 		-e "WEBSEED=$(WEBSEED)" \
+		-e "COMPRESSION_LEVEL=$(COMPRESSION_LEVEL)" \
 		$(ci_environment) \
 		"$(DOCKER_IMAGE)" \
 		debian-stretch

docker/entrypoint.sh

@@ -58,7 +58,7 @@ run_packer() {
 
 	mksquashfs build/rootfs "/images/$SQUASHFS_FILE" \
 		-comp lzo \
-		-Xcompression-level 9
+		-Xcompression-level $COMPRESSION_LEVEL
 
 	rm -rf build