Generate stub-generator tests in the build directory, and do not commit them to repository.

tests/stub-generator/src/MintMakerPromiseWithStubsTest.dart

 // Copyright (c) 2011, 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.
 
 // IsolateStubs=MintMakerPromiseWithStubsTest.dart:Mint,Purse
 
 #library("MintMakerPromiseWithStubsTest-generatedTest");
-#import("../../isolate/src/TestFramework.dart");
+#import("../../../tests/isolate/src/TestFramework.dart");
 
 interface Mint default MintImpl {
 
   Mint();
 
   Purse createPurse(int balance);
 
 }
 
 interface Purse default PurseImpl {
@@ skipping 101 matching lines @@
       expect.succeeded();
       print("##DONE##");
     });
   }
 
 }
 
 main() {
   runTests([MintMakerPromiseWithStubsTest.testMain]);
 }