Currently, CircleCI does not have complete support for Apple Silicon as we do not host any Apple Silicon machines on CircleCI Cloud. Additionally, Apple Silicon is not officially supported by CircleCI Runner.
With the current Intel hosts, you can still cross-compile for Apple Silicon which will allow you to build your apps as a "universal binary" on either CircleCI Cloud or Runner. The current suggestion is to export the binary as an artifact and test locally.
We are working towards adding this support in the future, but in the meantime please vote and comment on the below feature request as this will allow us to gauge interest in this feature: