Update the test harness to GN's location for the host's dart_bootstrap.

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 547 matching lines @@
     }
     return new CommandArtifact(commands, '$tempDir', 'application/dart-precompiled');
   }
 
   CompilationCommand computeCompilationCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
-    var exec = "$buildDir/dart_bootstrap";
+    var exec;
+    if (isAndroid && arch == 'arm') {
+      exec = "$buildDir/clang_x86/dart_bootstrap";
+    } else {
+      exec = "$buildDir/dart_bootstrap";
+    }
     var args = new List();
     args.add("--snapshot-kind=app-aot");
     if (useBlobs) {
       args.add("--snapshot=$tempDir/out.aotsnapshot");
       args.add("--use-blobs");
     } else {
       args.add("--snapshot=$tempDir/out.S");
     }
     if (isAndroid && arch == 'arm') {
       args.add('--no-sim-use-hardfp');
@@ skipping 264 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }