Treat R19 is a C preserved register, fixing crashing on Linux ARM64.

tools/utils.py

 # 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.
 
 # This file contains a set of utilities functions used by other Python-based
 # scripts.
 
 import commands
 import datetime
 import json
@@ skipping 608 matching lines @@
 def CheckedInSdkExecutable():
   name = 'dart'
   if IsWindows():
     name = 'dart.exe'
   elif GuessOS() == 'linux':
     arch = GuessArchitecture()
     if arch == 'mips':
       name = 'dart-mips'
     elif arch == 'arm':
       name = 'dart-arm'
+    elif arch == 'arm64':
+      name = 'dart-arm'
   return os.path.join(CheckedInSdkPath(), 'bin', name)
 
 
 def CheckedInSdkCheckExecutable():
   executable = CheckedInSdkExecutable()
   canary_script = os.path.join(os.path.dirname(os.path.realpath(__file__)),
                                'canary.dart')
   try:
     with open(os.devnull, 'wb') as silent_sink:
       if 0 == subprocess.call([executable, canary_script], stdout=silent_sink):
@@ skipping 25 matching lines @@
     os.chdir(self._working_directory)
 
   def __exit__(self, *_):
     print "Enter directory = ", self._old_cwd
     os.chdir(self._old_cwd)
 
 
 if __name__ == "__main__":
   import sys
   Main()