On drivers that do not support multi-platform builds (the default
`docker` driver), we do not support building attestations (unless using
the containerd store).
We need to check this feature before attempting to build using
attestations.
Also adds a test to ensure that attestations can be pushed to registries
at all, and that it adequately fails on the docker driver.
Signed-off-by: Justin Chadwell <me@jedevc.com>
Container driver wrote manifest digest that had a
mismatch with --iidfile output.
When --iidfile was set the --metadata-file was not
written.
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
Justin Chadwell