Observatory build fixes to dart executable finding code

tools/run_pub.py

 #!/usr/bin/env python
 # Copyright (c) 2015, 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.
 """Used to run pub before the SDK has been built"""
 
 import argparse
 import os
 import platform
 import subprocess
@@ skipping 10 matching lines @@
 def BuildArguments():
   result = argparse.ArgumentParser(usage=usage)
   result.add_argument("--package-root", help="package root", default=None)
   result.add_argument("--dart-executable", help="dart binary", default=None)
   return result
 
 def ProcessOptions(options, args):
   return ((options.package_root != None) and
           (options.dart_executable != None))
 
-def GetPrebuiltDartExecutablePath():
+def GetPrebuiltDartExecutablePath(suffix):
   osdict = {'Darwin':'macos', 'Linux':'linux', 'Windows':'windows'}
   system = platform.system()
   executable_name = 'dart'
   if system == 'Windows':
     executable_name = 'dart.exe'
   try:
     osname = osdict[system]
   except KeyError:
     print >>sys.stderr, ('WARNING: platform "%s" not supported') % (system)
     return None;
   return os.path.join(DART_ROOT,
                       'tools',
                       'testing',
                       'bin',
                       osname,
-                      executable_name)
+                      executable_name + suffix)
 
 def RunPub(dart, pkg_root, args):
   return subprocess.call([dart, '--package-root=' + pkg_root, PUB_PATH] + args)
 
 def TryRunningExecutable(dart_executable, pkg_root):
-  return subprocess.call([dart_executable,
-                          '--package-root=' + pkg_root,
-                          CANARY_PATH]) == 42
+  try:
+    return subprocess.call([dart_executable,
+                            '--package-root=' + pkg_root,
+                            CANARY_PATH]) == 42
+  except:
+    return False;
 
 def DisplayBootstrapWarning():
   print """\
 
 
 WARNING: Your system cannot run the prebuilt Dart executable. Using the
 bootstrap Dart executable will make Debug builds long.
 Please see Wiki for instructions on replacing prebuilt Dart executable.
 
 https://code.google.com/p/dart/wiki/ReplacingPrebuiltDartExecutable
 
 """
 
+def FindDartExecutable(fallback_executable, package_root):
+  # If requested, use the bootstrap binary instead of the prebuilt
+  # executable.
+  if os.getenv('DART_USE_BOOTSTRAP_BIN') != None:
+    return fallback_executable
+  # Try to find a working prebuilt dart executable.
+  dart_executable = GetPrebuiltDartExecutablePath('')
+  if TryRunningExecutable(dart_executable, package_root):
+    return dart_executable
+  dart_executable = GetPrebuiltDartExecutablePath('-arm')
+  if TryRunningExecutable(dart_executable, package_root):
+    return dart_executable
+  dart_executable = GetPrebuiltDartExecutablePath('-mips')
+  if TryRunningExecutable(dart_executable, package_root):
+    return dart_executable
+  # If the system cannot execute a prebuilt dart executable, use the bootstrap
+  # executable instead.
+  DisplayBootstrapWarning()
+  return fallback_executable
+
 def main():
   # Parse the options.
   parser = BuildArguments()
   (options, args) = parser.parse_known_args()
   if not ProcessOptions(options, args):
     parser.print_help()
     return 1
-  dart_executable = GetPrebuiltDartExecutablePath()
-  # If the system cannot execute the prebuilt dart executable, use the bootstrap
-  # executable instead.
-  if not TryRunningExecutable(dart_executable, options.package_root):
-    DisplayBootstrapWarning()
-    dart_executable = options.dart_executable
-  # If requested, use the bootstrap binary instead of the prebuilt
-  # executable.
-  if os.getenv('DART_USE_BOOTSTRAP_BIN') != None:
-    dart_executable = options.dart_executable
+  dart_executable = FindDartExecutable(options.dart_executable,
+                                       options.package_root)
   return RunPub(dart_executable, options.package_root, args)
 
 
 if __name__ == '__main__':
   sys.exit(main());