image_signing: Use "-b 256K" option for zstd squashfs compression

project-cheets-private CL: crrev/i/4381092

BUG=b:208763957
TEST=arc.AppLoadingPerf, etc.

BRANCH=none
Signed-off-by: Satoshi Niwa <niwa@google.com>
Cq-Depend: chrome-internal:4381092
Change-Id: I95fe539294793f6894a8e4cd8e2bde4bbcf43c04
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3351476
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Tested-by: Satoshi Niwa <niwa@chromium.org>
Auto-Submit: Satoshi Niwa <niwa@chromium.org>
Commit-Queue: Satoshi Niwa <niwa@chromium.org>
1 file changed