[gdbjit] Fix the way script name is accessed

Bug: chromium:1240661
Change-Id: I5552d63e3a50cd7f870af4ce135dba60cd33fc0a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3103322
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Auto-Submit: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76371}

test/mjsunit/regress/regress-crbug-1240661.js

+// Copyright 2021 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --gdbjit --allow-natives-syntax
+
+let f = new Function("boom");
+
+%PrepareFunctionForOptimization(f);
+%OptimizeFunctionOnNextCall(f);
+assertThrows(f, ReferenceError);