Add example using the Rust SGX SDK

[sbellem]

Resources:

• https://nixos.org/manual/nixpkgs/stable/#rust
• https://github.com/mozilla/nixpkgs-mozilla#rust-overlay
• https://christine.website/blog/how-i-start-nix-2020-03-08
• https://github.com/nix-community/naersk

Rough outline of steps:

• Set a standalone simple Rust enclave repo. We can extract the helloworld from the samplecode into its own repo, and change the relative path ...

[sbellem]

More up-to-date and additional resources:

• https://github.com/NixOS/nixpkgs/blob/master/doc/languages-frameworks/rust.section.md
• https://github.com/oxalica/rust-overlay
• https://discourse.nixos.org/t/how-can-i-set-up-my-rust-programming-environment/4501/10
• https://github.com/1000teslas/sparse_matrix/blob/master/flake.nix

[sbellem]

clang related: NixOS/nixpkgs#67725