sandbox: Add a build without CMDLINE

sandbox: Add a build without CMDLINE

Sometimes this breaks, so add a build to keep it working. Since sandbox
enables a lot of options, it is a good board to use. The new config is
created simply by copying the existing sandbox and turning off CMDLINE

Once we have tests for non-CMDLINE operation, this can be adjusted to
run those tests.

Create a new build which will be picked up by CI. Update the maintainer
entry as well.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>