Add rust::Vec push_back and emplace_back
diff --git a/gen/src/builtin.rs b/gen/src/builtin.rs
index 72b411c..41d037a 100644
--- a/gen/src/builtin.rs
+++ b/gen/src/builtin.rs
@@ -69,6 +69,7 @@
         include.array = true;
         include.new = true;
         include.type_traits = true;
+        include.utility = true;
         builtin.panic = true;
         builtin.unsafe_bitcopy = true;
     }