This fixes#13360 by adding fallback directories that are searched by
the CLI if the main executable cannot be found in the `libexec`
directory.
Release Notes:
- Added the fallback directories `lib/zed` and `lib/zed-editor` for the
main executable search in the CLI
([#13360](https://github.com/zed-industries/zed/issues/13360)).
---------
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
49dc63812a