Fix dangling pointer

tests/standalone/regress_26031_test.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+import 'dart:isolate';
+
+import "package:expect/expect.dart";
+
+void checkResolvedExecutable(String re) {
+  Expect.equals(Platform.resolvedExecutable, re);
+}
+
+main() {
+  var exitPort = new ReceivePort();
+  Isolate.spawn(checkResolvedExecutable,
+                Platform.resolvedExecutable,
+                onExit: exitPort.sendPort);
+  exitPort.listen((_) => exitPort.close());
+}