Change the main Dockerfile for sbcl to use make save too.

That building script does not rely on buildapp, which might be an advantage
in docker environments: first it's one less dependency, second, we have seen
weird error cases when using buildapp.

Dockerfile

@@ -26,7 +26,7 @@ FROM debian:stable-slim as builder
 
   RUN mkdir -p /opt/src/pgloader/build/bin \
       && cd /opt/src/pgloader \
-      && make
+      && make clones save
 
 FROM debian:stable-slim