Prepares for arm64 cross-build.

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 27 matching lines @@
   result = optparse.OptionParser()
   result.add_option("-m", "--mode",
       help='Build variants (comma-separated).',
       metavar='[all,debug,release]',
       default='debug')
   result.add_option("-v", "--verbose",
       help='Verbose output.',
       default=False, action="store_true")
   result.add_option("-a", "--arch",
       help='Target architectures (comma-separated).',
-      metavar='[all,ia32,x64,simarm,arm,simmips,mips,simarm64]',
+      metavar='[all,ia32,x64,simarm,arm,simmips,mips,simarm64,arm64,]',
       default=utils.GuessArchitecture())
   result.add_option("--os",
     help='Target OSs (comma-separated).',
     metavar='[all,host,android]',
     default='host')
   result.add_option("-t", "--toolchain",
     help='Cross-compiler toolchain path',
     default=None)
   result.add_option("-j",
       help='The number of parallel jobs to run.',
@@ skipping 24 matching lines @@
   if options.os == 'all':
     options.os = 'host,android'
   options.mode = options.mode.split(',')
   options.arch = options.arch.split(',')
   options.os = options.os.split(',')
   for mode in options.mode:
     if not mode in ['debug', 'release']:
       print "Unknown mode %s" % mode
       return False
   for arch in options.arch:
-    archs = ['ia32', 'x64', 'simarm', 'arm', 'simmips', 'mips', 'simarm64']
+    archs = ['ia32', 'x64', 'simarm', 'arm', 'simmips', 'mips',
+             'simarm64', 'arm64',]
     if not arch in archs:
       print "Unknown arch %s" % arch
       return False
   options.os = [ProcessOsOption(os) for os in options.os]
   for os in options.os:
     if not os in ['android', 'freebsd', 'linux', 'macos', 'win32']:
       print "Unknown os %s" % os
       return False
     if os != HOST_OS:
       if os != 'android':
@@ skipping 359 matching lines @@
             NotifyBuildDone(build_config, success=False, start=start_time)
             return 1
           else:
             NotifyBuildDone(build_config, success=True, start=start_time)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())