Export-image: Only disable metadata_csum feature if it's possibly enabled.

export-image/prerun.sh

@@ -50,8 +50,12 @@ ROOT_DEV=$(losetup --show -f -o ${ROOT_OFFSET} --sizelimit ${ROOT_LENGTH} ${IMG_
 echo "/boot: offset $BOOT_OFFSET, length $BOOT_LENGTH"
 echo "/:     offset $ROOT_OFFSET, length $ROOT_LENGTH"
 
+ROOT_FEATURES="^huge_file"
+if grep -q "metadata_csum" /etc/mke2fs.conf; then
+    ROOT_FEATURES="^metadata_csum,$ROOT_FEATURES"
+fi
 mkdosfs -n boot -F 32 -v $BOOT_DEV > /dev/null
-mkfs.ext4 -O ^metadata_csum,^huge_file $ROOT_DEV > /dev/null
+mkfs.ext4 -O $ROOT_FEATURES $ROOT_DEV > /dev/null
 
 mount -v $ROOT_DEV ${ROOTFS_DIR} -t ext4
 mkdir -p ${ROOTFS_DIR}/boot