systemd: fix nogroup

The special 65534 group is named nogroup (not nobody) in buildroot
tell systemd about that

Signed-off-by: Jérémy Rosen <jeremy.rosen@smile.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 9d912e619d48a7dfaed29d490bf389603974cfd2)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/systemd/systemd.mk

@@ -48,7 +48,8 @@ SYSTEMD_CONF_OPTS += \
 	-Dkexec-path=/usr/sbin/kexec \
 	-Dsulogin-path=/usr/sbin/sulogin \
 	-Dmount-path=/usr/bin/mount \
-	-Dumount-path=/usr/bin/umount
+	-Dumount-path=/usr/bin/umount \
+	-Dnobody-group=nogroup
 
 ifeq ($(BR2_PACKAGE_ACL),y)
 SYSTEMD_DEPENDENCIES += acl