lbu: fix sed command

fix #615

lbu.in

@@ -293,8 +293,8 @@ cmd_package() {
 		rm -f etc/lbu/packages.list
 	fi
 	# create tar archive
-	[ -f "$EXCLUDE_LIST" ] && sed '/^$/d' "$EXCLUDE_LIST" && excl="-X $EXCLUDE_LIST"
-	[ -f "$INCLUDE_LIST" ] && sed '/^$/d' "$INCLUDE_LIST" && incl="-T $INCLUDE_LIST"
+	[ -f "$EXCLUDE_LIST" ] && sed -i '/^$/d' "$EXCLUDE_LIST" && excl="-X $EXCLUDE_LIST"
+	[ -f "$INCLUDE_LIST" ] && sed -i '/^$/d' "$INCLUDE_LIST" && incl="-T $INCLUDE_LIST"
 	if [ -n "$VERBOSE" ]; then
 		echo "Archiving the following files:" >&2
 		# we dont want to mess the tar output with the