message: Use env::var_os("HOME") rather than env::var("HOME")
  Because the value is used to create a Path, there's no reason to go all
  the way validating it is utf-8 (although in practice, it almost
  certainly is, but it doesn't even matter).
diff: @@ -183,7 +183,7 @@ impl<'cfg> Compilation<'cfg> {
  // These are the defaults when DYLD_FALLBACK_LIBRARY_PATH isn't
  // set. Since Cargo is explicitly setting the value, make sure the
  // defaults still work.
  - if let Ok(home) = env::var("HOME") {
  + if let Some(home) = env::var_os("HOME") {
  search_path.push(PathBuf::from(home).join("lib"));
  }
  search_path.push(PathBuf::from("/usr/local/lib"));
  