gRPC-Core.podspec: init submodules, for nanopb
diff --git a/templates/gRPC-Core.podspec.template b/templates/gRPC-Core.podspec.template
index efe3738..a634d46 100644
--- a/templates/gRPC-Core.podspec.template
+++ b/templates/gRPC-Core.podspec.template
@@ -64,6 +64,7 @@
     s.source = {
       :git => 'https://github.com/grpc/grpc.git',
       :tag => "release-#{version.gsub(/\./, '_')}-objectivec-#{version}",
+      :submodules => true,
     }
 
     s.ios.deployment_target = '7.1'