Speed up the createSuper helper (#11401)

packages/babel-helpers/src/helpers.js

@@ -742,9 +742,11 @@ helpers.createSuper = helper("7.9.0")`
   import possibleConstructorReturn from "possibleConstructorReturn";
 
   export default function _createSuper(Derived) {
+    var hasNativeReflectConstruct = isNativeReflectConstruct();
+
     return function () {
       var Super = getPrototypeOf(Derived), result;
-      if (isNativeReflectConstruct()) {
+      if (hasNativeReflectConstruct) {
         // NOTE: This doesn't work if this.__proto__.constructor has been modified.
         var NewTarget = getPrototypeOf(this).constructor;
         result = Reflect.construct(Super, arguments, NewTarget);