[Request]: `container build -` for context-less build

### Feature or enhancement request details

The docker supports `docker build - < Dockerfile` for build without any filesystem entries.

As far as I know apple/container does not have feature to run build without any filesystem entries in context.

Currently it says `Error: context dir does not exist -`

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Start at the `container build` command handling and reproduce the reported `container build -` case with a Dockerfile supplied on standard input. Trace where `-` is treated as a context directory; done means a context-less build succeeds without requiring filesystem entries, with coverage for the stdin Dockerfile path.

Written by the indexing model from the issue text.