Clean before build

tools/snap/build.sh

@@ -38,4 +38,4 @@ docker run \
   -w "/certbot" \
   -e "PIP_EXTRA_INDEX_URL=http://localhost:8080" \
   "adferrand/snapcraft:${DOCKER_ARCH}-stable" \
-  snapcraft
+  /bin/bash -c "snapcraft clean && snapcraft"

tools/snap/build_dns.sh

@@ -54,6 +54,7 @@ IFS=","
 for DNS_PLUGIN in ${DNS_PLUGINS}; do
   pushd "${DNS_PLUGIN}"
   cp /snap-constraints.txt .
+  snapcraft clean
   snapcraft
   popd
 done