Cygwin: proc fd: pass along open mode when reopening file

The reopen code neglected to pass along the requested open
mode correctly.  This may end up reopening the file with
incorrect access mask, or duplicating the wrong pipe handle.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/syscalls.cc

@@ -1507,7 +1507,7 @@ open (const char *unix_path, int flags, ...)
       if (fh->dev () == FH_PROCESSFD && fh->pc.follow_fd_symlink ())
 	{
 	  /* Reopen file by descriptor */
-	  fh_file = fh->fd_reopen (flags);
+	  fh_file = fh->fd_reopen (flags, mode & 07777);
 	  if (!fh_file)
 	    __leave;
 	  delete fh;