Emit patched_sdk in the root output directory.

tools/testing/dart/compiler_configuration.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.
 
 library compiler_configuration;
 
 import 'dart:io' show Platform;
 
 import 'runtime_configuration.dart' show RuntimeConfiguration;
 
@@ skipping 210 matching lines @@
   }
 
   CompilationCommand computeCompilationCommand(
       String outputFileName,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
     var extraArguments = [
       '--sdk',
-      '$buildDir/obj/gen/patched_sdk',
+      '$buildDir/patched_sdk',
       '--link',
       '--target=vm',
       '--out',
       outputFileName
     ];
     return commandBuilder.getKernelCompilationCommand(
         'dartk',
         outputFileName,
         true,
         bootstrapDependencies(buildDir),
@@ skipping 586 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }