Fix build

runtime/vm/native_api_impl.cc

Index: runtime/vm/native_api_impl.cc
diff --git a/runtime/vm/native_api_impl.cc b/runtime/vm/native_api_impl.cc
index f08daa231336a3fcb505db7dde4d07dab584c9da..8a546e49d9def56049696ab8572c78dd1c8ae956 100644
--- a/runtime/vm/native_api_impl.cc
+++ b/runtime/vm/native_api_impl.cc
@@ -43,7 +43,7 @@ class IsolateSaver {
 };
 
 
-DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
+static bool PostCObjectHelper(Dart_Port port_id, Dart_CObject* message) {
   uint8_t* buffer = NULL;
   ApiMessageWriter writer(&buffer, allocator);
   bool success = writer.WriteCMessage(message);
@@ -56,6 +56,11 @@ DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
 }
 
 
+DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
+  return PostCObjectHelper(port_id, message);
+}
+
+
 DART_EXPORT bool Dart_PostInteger(Dart_Port port_id, int64_t message) {
   if (Smi::IsValid(message)) {
     return PortMap::PostMessage(new Message(
@@ -64,7 +69,7 @@ DART_EXPORT bool Dart_PostInteger(Dart_Port port_id, int64_t message) {
   Dart_CObject cobj;
   cobj.type = Dart_CObject_kInt64;
   cobj.value.as_int64 = message;
-  return Dart_PostCObject(port_id, &cobj);
+  return PostCObjectHelper(port_id, &cobj);
 }