Disable ext4 metadata_csum feature when building images

e2fsprogs v1.44.0+ will enable this feature by default.  However, our
3.8 kernels (for e.g. falco) cannot mount these images.

TEST=build test image, flash it, check with tune2fs, boot on falco

Change-Id: I05333f0f5feca97d3ee6caf3fb3e3c5c460e3ad1
Reviewed-on: https://chromium-review.googlesource.com/1014504
Commit-Ready: Kevin Cernekee <cernekee@chromium.org>
Tested-by: Kevin Cernekee <cernekee@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Aditya Kali <adityakali@google.com>
(cherry picked from commit 4b1db8f892d783dff9b280c965e6ea7bb9d97bd9)
Reviewed-on: https://chromium-review.googlesource.com/1025077
Reviewed-by: Kevin Cernekee <cernekee@chromium.org>
Commit-Queue: Kevin Cernekee <cernekee@chromium.org>
diff --git a/build_library/disk_layout_util.sh b/build_library/disk_layout_util.sh
index 04c2198..6f62967 100644
--- a/build_library/disk_layout_util.sh
+++ b/build_library/disk_layout_util.sh
@@ -418,7 +418,9 @@
     if [[ "${fs_uuid}" != "random" ]]; then
       uuid_option=( -U "${fs_uuid}" )
-    sudo mkfs.${fs_format} -F -q -O ext_attr \
+    # Disable metadata_csum for compatibility with 3.8 kernels
+    # (crbug.com/833643).
+    sudo mkfs.${fs_format} -F -q -O ext_attr,^metadata_csum \
         "${uuid_option[@]}" \
         -E lazy_itable_init=0 \
         -b ${fs_block_size} \