message: Enable block_trace middleware only on unix.
diff: #![doc(html_favicon_url = "https://wasmer.io/static/icons/favicon.ico")]
  #![doc(html_logo_url = "https://avatars3.githubusercontent.com/u/44205449?s=200&v=4")]
  +#[cfg(unix)]
  pub mod block_trace;
  pub mod call_trace;
  pub mod metering;
  