This commit is based on 748e89e703 with a small change to compile in
Linux.
Original changes:
- ethumb(_client) depend on `ethumb` option
- Remove ethumb(_client) from ignored subprojects
- Remove ethumb_client from default elementary dependencies
Additional changes:
- Surround `_elm_unneed_ethumb();` call in
`src/lib/elementary/elm_main.c` with `#ifdef HAVE_ETHUMB`.
Co-authored-by: Felipe Magno de Almeida <felipe@expertise.dev>