portability fixes: support building vboot on OpenBSD

This was done on OpenBSD 6.8.
Required packages are: e2fsprogs and gcc.

Change-Id: I86ec080e1ddb90053d81f1edd17d3406e7e737c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2903352
Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Commit-Queue: Patrick Georgi <pgeorgi@chromium.org>
9 files changed