Add PACKAGECONFIG 'selinux' for systemd. debug-shell.service starts
different shell according whether selinux is enabled.
(From OE-Core rev: 3d1aa27191fe4c21428eaf4ae036acb1496b7df7)
Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>