Add "create_bundle" target in order to support bundle with gn.

tools/gn/functions.h

Index: tools/gn/functions.h
diff --git a/tools/gn/functions.h b/tools/gn/functions.h
index 1341720150ab27a05686cd51151897e6c15dfbd5..3ce945e39fe42ed18a024e7fed034175cc42bc8a 100644
--- a/tools/gn/functions.h
+++ b/tools/gn/functions.h
@@ -89,6 +89,15 @@ Value RunBundleData(Scope* scope,
                     BlockNode* block,
                     Err* err);
 
+extern const char kCreateBundle[];
+extern const char kCreateBundle_HelpShort[];
+extern const char kCreateBundle_Help[];
+Value RunCreateBundle(Scope* scope,
+                      const FunctionCallNode* function,
+                      const std::vector<Value>& args,
+                      BlockNode* block,
+                      Err* err);
+
 extern const char kConfig[];
 extern const char kConfig_HelpShort[];
 extern const char kConfig_Help[];