[JS IR BE] Improve diagnostics in tests

js/js.translator/testData/_commonFiles/fail.kt

@@ -3,5 +3,9 @@ package kotlin
 // see StdLibTestBase.removeAdHocAssertions
 
 fun fail(message: String? = null): Nothing {
-    throw Exception(message)
+    // TODO: replace with next version when exception is supported properly
+    // throw Exception(message)
+
+    js("throw new Error(message)")
+    null!!
 }