Fix libtool requirement for autogen.sh. Re !72

.gitlab-ci.yml

@@ -14,7 +14,7 @@ stages:
   - archive
 
 prepare:
-  image: $REGISTRY_HUB:debian-9-base
+  image: $REGISTRY_HUB:debian-9-mini
   stage: prepare
   script:
   - find -path ./.git -prune -o -type f | xargs tools/style-check.sh