Leverage the power of the Gradle worker api

[Vampire]

I've did a quick search and it seems to me that you are not using the Gradle worker api. Though I think your plugin would be a good candidate for doing things with the worker api, especially when building for multiple target platforms, because then things can happen in parallel, like downloading multiple target platform JDKs, running multiple jlink instances in parallel and so on. This could help make builds faster as work can be done in parallel then.