Add an option to run `lake update`

[abdoo8080]

There are packages other than Mathlib that have post update hooks, without which the build fails. Please add an option to run lake update before running lake build.

[austinletson]

Thank you for submitting an issue. Could you provide an example workflow that fails?

lean-action doesn't typically run commands that would make modifications to files in the repository, such as updating the lake-manifest.json via lake update.

You might also be interested in lean-update, an action specifically designed for running lake update.