Make C++ cocoapods example work
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index fe50914..341ed8e 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -69,6 +69,8 @@
 
   s.default_subspecs = 'Interface', 'Implementation'
 
+  s.header_mappings_dir = 'include/grpcpp'
+
   s.subspec 'Interface' do |ss|
     ss.header_mappings_dir = 'include/grpcpp'