build_kernel_image: Update verity_hash_alg to "sha256"

Update default verity_hash_alg value to sha256. The verity hash
algorithm value in the other build scripts are already updated.
verity_hash_alg value on this script is used when this is
called from mod_image_for_recovery.sh, so the value
here needs to be updated as well.

BUG=chromium:1013235
TEST=Built a recovery test image with mod_image_for_recovery.sh,
deployed this to an octopus board and ran platform.DMVerity tast
test.
On the test result logs, <results_directory>/system_logs/messsages
dm_verity alg value is sha256.

Change-Id: I4d6bfff77b41c4000efb370319557a2433ceb314
Reviewed-on: https://chromium-review.googlesource.com/1893641
Tested-by: Betul Soysal <betuls@google.com>
Commit-Ready: Betul Soysal <betuls@google.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
(cherry picked from commit 86bea8dc9748905a0323836848525addaf22430a)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/4680070
Tested-by: Bob Moragues <moragues@chromium.org>
Commit-Queue: Bob Moragues <moragues@chromium.org>
Reviewed-by: YH Lin <yueherngl@chromium.org>
1 file changed