- The name of the subdirectory under site-lisp may not be exactly the
  same as the name of the package

- `(normal-top-level-add-subdirs-to-load-path)` adds every subdirectory
  of `default-directory` to the load-path, so users don't have to update
  their load-path for every package they install.

Closes Homebrew/homebrew#42309.