HACK(coral): gzip compression

BUG=none
TEST=none
BRANCH=none

Change-Id: Icf81e421c367e270dbb250a0c63816d89eda125b
Signed-off-by: Kazuhiro Inaba <kinaba@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2567836
Reviewed-by: Kazuhiro Inaba <kinaba@chromium.org>
Commit-Queue: Kazuhiro Inaba <kinaba@chromium.org>
Tested-by: Kazuhiro Inaba <kinaba@chromium.org>
Auto-Submit: Kazuhiro Inaba <kinaba@chromium.org>