exa is written in [Rust](http://www.rust-lang.org). It compiles with Rust 0.11, the latest version - 0.10 will not do, as there have been too many breaking changes since. You will also need [Cargo](http://crates.io), the Rust package manager. Once you have them both set up, a simple `cargo build` will pull in all the dependencies and compile exa.