Support building engine library for desktop multiplatform app

[hellais]

Currently we don't have tooling to build a jar library that we can load in a kotlin multiplatform desktop app.

Here there is a PR that supposedly does this, but might need some work to get it functioning: https://github.com/golang/mobile/pull/90/files

[sdsantos]

Here is a repository that proves that we can use a go function inside a KMM desktop app: https://github.com/sdsantos/go-desktop/

It uses code found on this github project. Instead of JNI, it uses JNR, to avoid having to right C code and compile it. Here there's a brief explanation on the subject: https://youtu.be/DnaXcXRb7XA?feature=shared&t=474

[sdsantos]

Here is the branch with the proof-of-concept: https://github.com/ooni/probe-multiplatform/tree/desktop-with-jar
It uses the oonimkall engine through a JAR file generated with this gomobile fork: https://github.com/hellais/mobile/tree/plainjava-pr