Merge branch 'master' into no-root-build

Dockerfile

 FROM scratch
-ADD archlinux.tar /
+ADD archlinux.tar.xz /
 
 # manually run all alpm hooks that can't be run inside the fakechroot
 RUN ldconfig && update-ca-trust && locale-gen

Makefile

@@ -19,7 +19,10 @@ rootfs: hooks
 	tar --numeric-owner --xattrs --acls --exclude-from=exclude -C $(BUILDDIR) -c . -f archlinux.tar
 	rm -rf $(BUILDDIR) alpm-hooks
 
-docker-image: rootfs
+compress-rootfs: rootfs
+	xz archlinux.tar
+
+docker-image: compress-rootfs
 	docker build -t $(DOCKER_ORGANIZATION)/$(DOCKER_IMAGE) .
 
 docker-image-test: docker-image