Don't have svn ls block waiting for password

If user is unauthenticated, svn ls would just hang waiting at
"Password for 'User':", now it'll correctly fail with
"svn: Can't get password".

R=iannucci@chromium.org
BUG=323300,346472

Review URL: https://codereview.chromium.org/178763003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@253004 0039d316-1c4b-4281-b951-d872f2087c98

win_toolchain/get_toolchain_if_necessary.py

@@ -121,7 +121,7 @@ def HaveSrcInternalAccess():
   """Checks whether access to src-internal is available."""
   with open(os.devnull, 'w') as nul:
     if subprocess.call(
-        ['svn', 'ls',
+        ['svn', 'ls', '--non-interactive',
          'svn://svn.chromium.org/chrome-internal/trunk/src-internal/'],
         shell=True, stdin=nul, stdout=nul, stderr=nul) == 0:
       return True