tweak sed, make compile_grpc.sh executable

scripts/compile_grpc.sh

@@ -2,6 +2,6 @@
 source ./install.sh
 pushd exo/networking/grpc
 python3 -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. node_service.proto
-sed -i "s/import\ node_service_pb2/from . &/" node_service_pb2_grpc.py
+sed -i '' "s/import\ node_service_pb2/from . &/" node_service_pb2_grpc.py
 popd