Set execute permissions on sky_server after download.

BUG=
[email protected]

Review URL: https://codereview.chromium.org/886543004

tools/download_sky_server

@@ -3,18 +3,22 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import os
+import stat
 import subprocess
 
 from webkitpy.common.system import filesystem
 from webkitpy.common.webkit_finder import WebKitFinder
 
 finder = WebKitFinder(filesystem.FileSystem())
 
+output_file_ = finder.path_from_chromium_base('out', 'downloads', 'sky_server')
 subprocess.call([
     'download_from_google_storage',
     '--no_resume',
     '--no_auth',
     '--bucket', 'mojo',
     '--sha1_file', finder.path_from_chromium_base('sky', 'tools', 'skygo', 'sky_server.sha1'),
-    '--output', finder.path_from_chromium_base('out', 'downloads', 'sky_server')
+    '--output', output_file_
 ])
+os.chmod(output_file_, os.stat(output_file_).st_mode | stat.S_IEXEC)