bitbucket-pipe-release multi-platform & build kit support

[Adam Lofthouse-Hill]

I am trying to use `bitbucket-pipe-release:5.80` which is supposed to include multi-platform support. However, when I try to use this on your own cloud runners I get the following error in my pipeline:

```

ERROR: Error response from daemon: authorization denied by plugin pipelines: --privileged=true is not allowed

125

```

I believe this is because you disable the buildx support for the Docker service when using the cloud runners. But I see no mention of this in the documentation for bitbucket-pipe-release and it seems strange that you would be publishing a pipe that doesn't work on your own runners.

[Igor Stoyanov]

@Adam Lofthouse-Hill hi. Thanks for your question.

Multi-platform build feature is not officially supported yet.

Regards, Igor