tests: futility: Fix build failure due to missing libzip

The test programs do need libzip.

BUG=chromium:953993
TEST=emerge vboot_reference
BRANCH=None

Change-Id: I7347a0d192874b9eddeef4448e2d7b2d1e317fec
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1577348
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1577349
1 file changed