dir.c: fallback to ASCII-8BIT

* dir.c (push_glob): fallback to ASCII-8BIT for the case non-ascii
  path name exists.  failed with LANG=C, on MacOS X which has a
  localized symlink on the root directory.

git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/trunk@44834 b2dd03c8-39d4-4d8f-98ff-823fe69b080e