more cautious building of grpc

get-packages.sh

@@ -27,7 +27,7 @@ function main()
 
 
 	cd $here_dir/third-party/grpc
-	if [[ ! -x third_party/protobuf/src/protoc ]]; then
+	if [[ ! -x third_party/protobuf/src/protoc ]] && [[ -x /usr/local/bin/protoc ]] ; then
 		if [[ ! -f Makefile ]]; then
 			cmake .
 		fi