message: First look in the local path for the wasm-opt binary. Use whatever binary is found and assume it works
diff: use crate::child;
  use crate::install::{self, Tool};
  use crate::PBAR;
  -use binary_install::Cache;
  +use binary_install::{Cache, Download};
  use std::path::Path;
  use std::process::Command;
  @@ -58,6 +58,16 @@ pub fn find_wasm_opt(
  cache: &Cache,
  install_permitted: bool,
  ) -> Result<install::Status, failure::Error> {
  + // First attempt to look up in PATH. If found assume it works.
  + if let Ok(path) = which::which("wasm-opt") {
  + PBAR.info(&format!("found wasm-opt at {:?}", path));
  +
  + match path.as_path().parent() {
  + Some(path) => return Ok(install::Status::Found(Download::at(path))),
  + _ => {}
  + }
  + }
  +
  let version = "version_78";
  Ok(install::download_prebuilt(
  &install::Tool::WasmOpt,
  