systemd: add compatibility symlink for 'shutdown'

In addition to the 'halt', 'poweroff', 'reboot' symlinks pointing to
systemctl, add 'shutdown'.

Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 36ed046623129bb879ef50cd40dcc65b27c9da0f)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/systemd/systemd.mk

@@ -329,6 +329,7 @@ define SYSTEMD_INSTALL_INIT_HOOK
 	ln -fs ../bin/systemctl $(TARGET_DIR)/sbin/halt
 	ln -fs ../bin/systemctl $(TARGET_DIR)/sbin/poweroff
 	ln -fs ../bin/systemctl $(TARGET_DIR)/sbin/reboot
+	ln -fs ../bin/systemctl $(TARGET_DIR)/sbin/shutdown
 	ln -fs ../../../lib/systemd/system/multi-user.target \
 		$(TARGET_DIR)/etc/systemd/system/default.target
 endef