Allow NO_CACHE=1 in build-image.sh to force clean build

scripts/build-image.sh

@@ -12,6 +12,13 @@ if [[ -f ".env" ]]; then
 fi
 
 IMAGE_TAG="${IMAGE_TAG:-taler-stack:build}"
+# Allow forcing a clean rebuild to pick up fresh vendor tarballs
+NO_CACHE="${NO_CACHE:-0}"
+
+CACHE_FLAG=()
+if [[ "${NO_CACHE}" == "1" ]]; then
+  CACHE_FLAG+=(--no-cache)
+fi
 
 docker build \
   --build-arg GNUNET_REF="${GNUNET_REF:-v0.26.1}" \
@@ -22,6 +29,7 @@ docker build \
   --build-arg MERCHANT_TARBALL_URL="${MERCHANT_TARBALL_URL:-}" \
   --build-arg LIBEUFIN_REF="${LIBEUFIN_REF:-master}" \
   --build-arg LIBEUFIN_TARBALL_URL="${LIBEUFIN_TARBALL_URL:-}" \
+  "${CACHE_FLAG[@]}" \
   -t "${IMAGE_TAG}" .
 
 echo "Built image ${IMAGE_TAG}"