Use DLL_EXTENSION on bindgen to allow for non-Linux
requested to merge SalvatoreT/uniffi-kotlin-multiplatform-bindings:salvatoret/22/macos-fix-gradle-setup into main
The .so extension is for Linux, but Rust has a handy constant to allow
for other operating systems.
There are other issues still open, but this takes care of the syncing issue.
Closes #22 (closed) Closes #3 (closed)