No need to prin DU from Makefile in LFS

We now print the disk usage from the scriptlet, so printing
again from the Makefile results in a duplicated line. Remove
the printing if book=lfs

common/libs/func_wrt_Makefile

@@ -322,7 +322,9 @@ wrt_RunAsRoot() {                  # Some scripts must be run as root..
 cat << EOF
 	@export ${MOUNT_ENV}=\$(MOUNT_PT) && \\
 	${PROGNAME}-commands/`dirname $file`/\$@ >>logs/\$@$version 2>&1 && \\
-	\$(PRT_DU) >>logs/\$@$version
+	if [ "${PROGNAME}" != lfs ]; then \\
+	    \$(PRT_DU) >>logs/\$@$version; \\
+	fi
 EOF
 ) >> $MKFILE.tmp
 }