Add unit test

Author: boingoing

test/Bugs/bug_OS17530048.js

@@ -0,0 +1,8 @@
+//-------------------------------------------------------------------------------------------------------
+// Copyright (C) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE.txt file in the project root for full license information.
+//-------------------------------------------------------------------------------------------------------
+
+(a = () => 1) => 2;
+(function(){})()
+console.log('pass');

test/Bugs/rlexe.xml

@@ -489,4 +489,11 @@
       <files>bug17785360.js</files>
     </default>
   </test> 
+  <test>
+    <default>
+      <files>bug_OS17530048.js</files>
+      <tags>exclude_jshost</tags>
+      <compile-flags>-force:deferparse -parserstatecache -useparserstatecache</compile-flags>
+    </default>
+  </test>
 </regress-exe>