GN: Use build directory for CD for scripts

tools/gn/test_with_scope.cc

Index: tools/gn/test_with_scope.cc
diff --git a/tools/gn/test_with_scope.cc b/tools/gn/test_with_scope.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e83c99cb060e2bb742744061ac83f63f728f5c38
--- /dev/null
+++ b/tools/gn/test_with_scope.cc
@@ -0,0 +1,15 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tools/gn/test_with_scope.h"
+
+TestWithScope::TestWithScope()
+    : build_settings_(),
+      toolchain_(Label(SourceDir("//toolchain/"), "tc")),
+      settings_(&build_settings_, &toolchain_, std::string()),
+      scope_(&settings_) {
+}
+
+TestWithScope::~TestWithScope() {
+}