Regenerate pub using the latest version of async-await.

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

Index: sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
diff --git a/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart b/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
index 7e1a7ae98bc164ca116c76f7cc3486fcd67c8813..bd2243f4a8c22f5259e328451f4b346094316f5b 100644
--- a/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
+++ b/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
@@ -20,7 +20,7 @@ Future<Map> getEnvironment() {
       join0(x0) {
         var separator = x0;
         var path = "${Platform.environment["PATH"]}${separator}${binDir}";
-        getPubTestEnvironment().then((x1) {
+        new Future.value(getPubTestEnvironment()).then((x1) {
           try {
             var environment = x1;
             environment["PATH"] = path;