ansible: update zlib fetch URL

Once zlib releases a new version they remove the older one and move it
to https://www.zlib.net/fossils/. Use this more stable URL to fetch the
zlib source when building containers.

Author: richardlau

ansible/roles/docker/templates/ubuntu1804_sharedlibs.Dockerfile.j2

@@ -94,7 +94,7 @@ ENV ZLIB12DIR /opt/zlib_$ZLIBVER
 
 RUN mkdir -p /tmp/zlib_$ZLIBVER && \
     cd /tmp/zlib_$ZLIBVER && \
-    curl -sL https://zlib.net/zlib-$ZLIBVER.tar.gz | tar zxv --strip=1 && \
+    curl -sL https://zlib.net/fossils/zlib-$ZLIBVER.tar.gz | tar zxv --strip=1 && \
     ./configure --prefix=$ZLIB12DIR && \
     make -j 6 && \
     make install && \