Support Gradle incremental annotation processing

[wmdietl]

Would it be possible to let the type checkers be incremental annotation processors?
Are there any risks that an incremental compile would introduce an unsoundness?

See the Gradle Manual: https://docs.gradle.org/current/userguide/java_plugin.html#sec:incremental_annotation_processing

I also found this library that seems to make this very easy: https://github.com/tbroyer/gradle-incap-helper

If it is not possible to do this, document it in the manual.