message: Borrow webpack_config and add comment
diff: @@ -160,11 +160,12 @@ fn setup_build(target: &Target) -> Result<(Command, PathBuf, Bundle), failure::E
  command.arg(format!("--wasm-binding={}", bundle.get_wasm_binding()));
  let webpack_config_path = if let Some(webpack_config) = &target.webpack_config {
  - Some(PathBuf::from(webpack_config.clone()))
  + Some(PathBuf::from(&webpack_config))
  } else if target.site.is_none() {
  message::warn("In Wrangler v1.6.0, you will need to include a webpack_config field in your wrangler.toml to build with a custom webpack configuration.");
  Some(PathBuf::from("webpack.config.js".to_string()))
  } else {
  + // don't use `webpack.config.js` if this project is a site
  None
  };
  