Export assignment expression must not track variables (#4660)

Only export the result of the assignment expression. This value cannot be changed later.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

tests/jerry/es.next/module-namespace-02.mjs

@@ -14,6 +14,7 @@
  */
 
 import def, {a} from "./module-namespace-03.mjs"
+/* Nothing is tracked, only the result value is exported. */
 export default def
 export {a}