[releng] Build the environment as required

build.sh

@@ -9,6 +9,13 @@ HASH=$(hg -R "$ROOT" --debug id -i)
 # Cleanup
 hg -R "$ROOT" purge --all
 
+BUILDER=$(docker images | grep -o -E '^logilab/ld-build-env(\s)+latest' | wc -l)
+
+if [ "$BUILDER" -lt "1" ]; then
+  echo "=> Build environment must be created"
+  "$ROOT/.releng/build-env.sh"
+fi
+
 # Execute the build
 docker run -it --rm --user=$(id -u) --group-add=$(id -g) -v "$ROOT:/src" -e "HOME=/npm" "logilab/ld-build-env:latest" /src/.releng/build-src.sh