Updating the Android NDK in Rust 1.68

[NewsBot]

A new Rust blog post/announcement has been posted!

We are pleased to announce that Android platform support in Rust will be modernized in Rust 1.68 as we update the target NDK from r17 to r25. As a consequence the minimum supported API level will increase from 15 (Ice Cream Sandwich) to 19 (KitKat).

In NDK r23 Android switched to using LLVM's libunwind for all architectures. This meant that

1. If a project were to target NDK r23 or newer with previous versions of Rust a workaround would be required to redirect attempts to link against libgcc to instead link against libunwind. Following this update this workaround will no longer be necessary.
2. If a project uses NDK r22 or older it will need to be updated to use r23 or newer. Information about the layout of the NDK's toolchain can be found https://blog.rust-lang.org/2023/01/09/android-ndk-update-r25.html