Updates build scripts for updated android_tools.

tools/build.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, 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.
 #
 
 import optparse
 import os
 import re
@@ skipping 167 matching lines @@
   CheckDirExists(THIRD_PARTY_ROOT, 'third party tools');
   android_tools = os.path.join(THIRD_PARTY_ROOT, 'android_tools')
   CheckDirExists(android_tools, 'Android tools')
   android_ndk_root = os.path.join(android_tools, 'ndk')
   CheckDirExists(android_ndk_root, 'Android NDK')
 
   # Set up the directory of the Android NDK cross-compiler toolchain.
   toolchain_arch = 'arm-linux-androideabi-4.6'
   if target_arch == 'ia32':
     toolchain_arch = 'x86-4.6'
-  toolchain_dir = 'linux-x86'
+  toolchain_dir = 'linux-x86_64'
   android_toolchain = os.path.join(android_ndk_root,
       'toolchains', toolchain_arch,
       'prebuilt', toolchain_dir, 'bin')
   CheckDirExists(android_toolchain, 'Android toolchain')
 
   return android_toolchain
 
 
 def Execute(args):
   process = subprocess.Popen(args)
@@ skipping 206 matching lines @@
           process.wait()
           if process.returncode != 0:
             print "BUILD FAILED"
             return 1
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())