Fix failed to find release-builder dockerfile & push specific tag (#870)

hack/release.sh

@@ -155,7 +155,7 @@ tag_and_release() {
     git tag $gittag
     
     # push tag
-    git push --tags
+    git push $gittag
 
     # create gh release
     gothub release \
@@ -331,7 +331,7 @@ fi
 release_environment_check $version $chartsrepo
 
 # Build release-builder image
-docker build -t fission-release-builder .
+docker build -t fission-release-builder -f $GOPATH/src/github.com/fission/fission/hack/Dockerfile .
 
 # Build all binaries & container images in docker
 # Here we mount docker.sock into container so that docker client can communicate with host docker daemon.