lighttpd: Add systemd tmpfile to fix lighttpd systemd boot

Problem starting lighttpd application with systemd.

/usr/sbin/lighttpd -D -f /etc/lighttpd/lighttpd.conf
2018-06-22 11:21:34: (server.c.733) opening errorlog '/var/log/lighttpd-error.log' failed: Permission denied
2018-06-22 11:21:34: (server.c.1420) Opening errorlog failed. Going down.

Lighttpd can not write the 'lighttpd-access.log' and 'lighttpd-error.log' files
to the directory '/var/log/'.

When using systemd the directory '/var/log' does not allow the user www-data to
write.

To correct the problem, we add /usr/lib/tmpfiles.d/lighttpd.conf.
This file create the 'lighttpd-access.log' and 'lighttpd-error.log' files  with
the permission

Signed-off-by: Laurent Hartanerot <laurent.hartanerot@atos.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/lighttpd/lighttpd.mk

@@ -96,6 +96,9 @@ define LIGHTTPD_INSTALL_INIT_SYSTEMD
 
 	ln -fs ../../../../usr/lib/systemd/system/lighttpd.service \
 		$(TARGET_DIR)/etc/systemd/system/multi-user.target.wants/lighttpd.service
+
+	$(INSTALL) -D -m 644 package/lighttpd/lighttpd_tmpfiles.conf \
+		$(TARGET_DIR)/usr/lib/tmpfiles.d/lighttpd.conf
 endef
 
 $(eval $(autotools-package))

package/lighttpd/lighttpd_tmpfiles.conf

@@ -0,0 +1,2 @@
+f /var/log/lighttpd-access.log 0640 www-data www-data -
+f /var/log/lighttpd-error.log 0640 www-data www-data -