Get binstubs working on Windows.

sdk/lib/_internal/pub/test/global/binstubs/reactivate_removes_old_executables_test.dart

 // Copyright (c) 2014, 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 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
+import 'utils.dart';
 
 main() {
   initConfig();
   integration("removes previous binstubs when reactivating a package", () {
     d.dir("foo", [
       d.pubspec({
         "name": "foo",
         "executables": {
           "one": null,
           "two": null
@@ skipping 14 matching lines @@
           // Remove "one".
           "two": null
         }
       }),
     ]).create();
 
     schedulePub(args: ["global", "activate", "--source", "path", "../foo"]);
 
     d.dir(cachePath, [
       d.dir("bin", [
-        d.nothing("one"),
-        d.matcherFile("two", contains("two"))
+        d.nothing(binStubName("one")),
+        d.matcherFile(binStubName("two"), contains("two"))
       ])
     ]).validate();
   });
 }