Minimum changes for Android support

[madsodgaard]

This has the bare minimum changes needed to make the project work on Android.

I have tested it with the upcoming official Android SDK and works 👍

Credit should be given to #144

[lhoward]

Notes:

• JavaKit: Passing objects between threads #157 is not addressed; this will cause issues in any complex Android application that passes objects between threads
• if you target the correct NDK version you should be able to link against libnativehelper.so rather than dynamically loading it (cc @finagolfin)

[ktoso]

• JavaKit: Passing objects between threads #157 is still unresolved so that's tracked by that

For

if you target the correct NDK version you should be able to link against libnativehelper.so rather than dynamically loading it (cc @finagolfin)

Would you mind filing a new issue please @lhoward ?

[madsodgaard]

• if you target the correct NDK version you should be able to link against libnativehelper.so rather than dynamically loading it (cc @finagolfin)

I think you mean Android SDK and not NDK, right? The libnativehelper functions were exported in API 31. And we can't do conditionally linking based on version via SwiftPM unfortunately.

[lhoward]

I do probably mean that, Android development details have been swapped out of my brain :) Anyway, if you need to dynamically load it, so be it.