core: Don't strip setuid bits when creating files

This ugly regression occurred because I overlooked the fact that our
chown() invocation would strip off setuid.

tests/test-setuid.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+#
+# Copyright (C) 2013 Colin Walters <walters@verbum.org>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+set -e
+
+echo "1..1"
+
+. $(dirname $0)/libtest.sh
+
+setup_test_repository "bare"
+
+cd ${test_tmpdir}
+cat > test-statoverride.txt <<EOF
++2048 /abinary
+EOF
+$OSTREE checkout test2 test2-checkout
+touch test2-checkout/abinary
+chmod a+x test2-checkout/abinary
+(cd test2-checkout && $OSTREE commit -b test2 -s "with statoverride" --statoverride=../test-statoverride.txt)
+rm -rf test2-checkout
+$OSTREE checkout test2 test2-checkout
+test -u test2-checkout/abinary