Bundle the config JSON into the tnull binary

The issue currently is that the tnull binary depends on the config.json
file directly, but that would need to be put somewhere in the RTD image
for it to be readable. If we just build it into the binary instead, all
will be well. This config isn't supposed to be mutable inside the RTD
container anyway.

BUG=chromium:1149702
TEST=local runs

Change-Id: If3845ae7b621953fcec1d8322c44bb6d516b75f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/tnull/+/2558974
Reviewed-by: Prathmesh Prabhu <pprabhu@google.com>
Commit-Queue: Sean Abraham <seanabraham@chromium.org>
Tested-by: Sean Abraham <seanabraham@chromium.org>
5 files changed