Add ability to ignore `[build-dependencies]` when checking for licenses

[liss-h]

There is already an option to ignore dev-dependencies when checking for licenses (enabled by default), but there does not seem to be a way to ignore build-dependencies. It would be very helpful if that could be implemented.

This was originally requested in the following issue, but seems to have been ignored without comment:

I wish to add build-allow for [build-dependencies]

Originally posted by @kazuk in #413

I've found some other open issues that seem somewhat related, but they look like they focus more on [bans] and not the license checks.