add example of how to package a wrap.sh

[mutantbob]

I have an android application that crashes inside slice::from_raw_parts . I altered my app to set RUST_BACKTRACE=1, but this still did not give me a stack trace. The next idea I had was to use the wrap.sh mechanism documented at https://developer.android.com/ndk/guides/wrap-script to set RUST_BACKTRACE=1 before it starts.

Unfortunately, I am struggling to figure out what to put in my Cargo.toml to include a custom wrap.sh into the apk generated by cargo apk build

It would be helpful if the documentation included an example of how to include a wrap.sh in the .apk.

Until then, I am struggling to figure out what steps cargo apk is taking to build the .apk in hopes of running those steps manually to include wrap.sh.

[MarijnS95]

Afaik it's quite common to set this variable as the first thing inside the main function:

https://github.com/rust-mobile/xbuild/blob/5662af28119361550f212f9a8067abb1c5ee3902/xbuild/template/lib.rs#L26

(that would be fn android_main() if using android-activity.

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According to https://developer.android.com/ndk/guides/wrap-script#packaging_wrapsh wrap.sh should be in the architecture-specific lib/xxx folders. cargo-apk already allows packaging arbitrary .so files into that folder when configured via runtime_libs, but I don't remember whether cargo-apk currently visits and packages any non *.so's although you can definitely try (and otherwise submit a PR -including the requested sample- to make that possible).

Also don't forget to set debuggable = true on the application.