package/usbguard: enforce the right permissions on the configuration file

package/usbguard: enforce the right permissions on the configuration file

Only 0600 rights are allowed for the rules.conf. This file is read when the
usbguard daemon starts and will prevent it to run otherwise.

As Git only tracks the executable bit, setting the right permissions in the
package makefile is the cleanest solution, in particular when providing this
file from a rootfs overlay.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>