run tests sequentially

packages/flutter_tools/test/init_test.dart

@@ -4,6 +4,8 @@
 
 // This test can take a while due to network requests
 @Timeout(const Duration(seconds: 60))
+library init_test;
+
 import 'dart:io';
 
 import 'package:args/command_runner.dart';

packages/flutter_tools/tool/travis.sh

@@ -12,4 +12,4 @@ pub global activate tuneup
 pub global run tuneup check
 
 # And run our tests.
-pub run test
+pub run test -j1