make-image: Don't require TTY

debootstrap/make-image.sh

@@ -9,7 +9,12 @@ if [ -n "$DOCKER_REGISTRY" ]; then
   IMAGE="${DOCKER_REGISTRY}/${IMAGE}"
 fi
 
-docker run -it --rm \
+opts=
+if [ -t 1 ] && [ -t 0 ]; then
+  opts=-t
+fi
+
+docker run -i $opts --rm \
   --privileged \
   -e "TARBALL=$TARBALL" \
   -v "$(pwd):/work" -w "/work" \