support for standard Docker/OCI in buildbox

Context

We're not able to use Bazel client remote execution on the provided hosttools buildbox because they don't have the dependencies needed for our builds. The only way to get this to work is to build and install the buildbox components on our existing Ubuntu 18.04 worker images. This is a major hurdle to build and install successfully.

bazel only works with hosttools for normal operation as the action input trees are not complete root directories. If you want to run builds in your own Docker/OCI container specified via platform property, another runner would be required. There is buildbox-run-oci, however, I think that's still considered experimental and doesn't directly support this use case yet.

Task Description

This ticket is to request support for our own Docker/OCI containers by buildbox.

Acceptance Criteria

Bazel clients are able to provide our own Docker container to be used by buildbox

Consider whether the following are required, and complete if so:

• Unit tests
• Metrics
• Documentation update(s)