ensure action image entrypoint is executable

image/Dockerfile

@@ -9,6 +9,6 @@ RUN apt-get update \
       zip \
 &&  gem install --no-document fpm -v 1.15.1
 
-COPY entrypoint.sh /entrypoint.sh
+ADD --chmod=755 entrypoint.sh /entrypoint.sh
 
 ENTRYPOINT ["/entrypoint.sh"]