getting backtrace from panics in the enclave

Hi,
Do you have any ideas on how I can get a backtrace when I have a panic in the enclave?

Right now all I get is something like this:
```
thread panicked at 'Box', /root/.cargo/registry/src/github.com-1ecc6299db9ec823/hashbrown-0.3.0/src/raw/mod.rs:1078:9
```

Start with the enclave panic output shown in the issue, including the hashbrown raw.rs:1078:9 location, and investigate how backtraces are handled in the Rust SGX enclave environment. Review the panic and runtime entry points involved; done means documenting or enabling a reproducible way to obtain useful enclave backtraces.

Written by the indexing model from the issue text.