Make pub's binstubs resilient to changes in snapshot format.

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

Index: sdk/lib/_internal/pub/test/global/binstubs/utils.dart
diff --git a/sdk/lib/_internal/pub/test/global/binstubs/utils.dart b/sdk/lib/_internal/pub/test/global/binstubs/utils.dart
index e52a1ebdfcd0798cb3595d6317ae0aba7930ccaf..ca70df8146bbc111fe445455f20025d69b395e60 100644
--- a/sdk/lib/_internal/pub/test/global/binstubs/utils.dart
+++ b/sdk/lib/_internal/pub/test/global/binstubs/utils.dart
@@ -2,12 +2,22 @@
 // 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:async';
 import 'dart:io';
 
-/// Returns the name of the shell script for a binstub named [name].
-///
-/// Adds a ".bat" extension on Windows.
-binStubName(String name) {
-  if (Platform.operatingSystem == "windows") return "$name.bat";
-  return name;
+import 'package:path/path.dart' as p;
+
+import '../../test_pub.dart';
+
+/// The buildbots do not have the Dart SDK (containing "dart" and "pub") on
+/// their PATH, so we need to spawn the binstub process with a PATH that
+/// explicitly includes it.
+Future<Map> getEnvironment() async {
+  var binDir = p.dirname(Platform.executable);
+  var separator = Platform.operatingSystem == "windows" ? ";" : ":";
+  var path = "${Platform.environment["PATH"]}$separator$binDir";
+
+  var environment = await getPubTestEnvironment();
+  environment["PATH"] = path;
+  return environment;
 }