[FIR JS] Prepare the test data for FIR

compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/native.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNREACHABLE_CODE
 // unreachable code suppressed due to KT-9586
 
@@ -38,4 +39,4 @@ external object O {
 
     fun foo(s: String): String
     fun bar(s: String): String = definedExternally
-}
+}