gnulib: import chown

A few sims use this to emulate chown syscalls.

gnulib/import/fchown-stub.c

@@ -0,0 +1,34 @@
+/* Change ownership of a file.
+   Copyright (C) 2004-2021 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert, 2004.  */
+
+#include <config.h>
+
+#include <sys/types.h>
+#include <errno.h>
+
+/* A trivial substitute for 'fchown'.
+
+   DJGPP 2.03 and earlier (and perhaps later) don't have 'fchown',
+   so we pretend no-one has permission for this operation. */
+
+int
+fchown (int fd, uid_t uid, gid_t gid)
+{
+  errno = EPERM;
+  return -1;
+}