use "sort|uniq" instead of "sort -u" to work with the MSVC ports

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14019 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#5833: README.win32 can leave the wrong flexlink in the path

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14020 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02