base-files: add missing $IPKG_INSTROOT to restorecon call

Update to overlooked v2 version of Dominick Grift's patch.

Fixes: 5109bd164c ("base-files: address sed in-place without SELinux awareness")
Signed-off-by: Daniel Golle <[email protected]>

package/base-files/files/lib/functions.sh

@@ -386,7 +386,9 @@ group_add_user() {
 	echo "$grp" | grep -q ":$" && delim=""
 	[ -n "$IPKG_INSTROOT" ] || lock /var/lock/passwd
 	sed -i "s/$grp/$grp$delim$2/g" ${IPKG_INSTROOT}/etc/group
-	selinuxenabled 2>/dev/null && restorecon /etc/group
+	if [ -x /usr/sbin/selinuxenabled ] && selinuxenabled; then
+		selinuxenabled 2>/dev/null && restorecon ${IPKG_INSTROOT}/etc/group
+	fi
 	[ -n "$IPKG_INSTROOT" ] || lock -u /var/lock/passwd
 }