> We don't have [:optional, :run] deps in core
That's actually false, there's
```rb
Formula/qca.rb: depends_on :gpg => [:optional, :run] # qca-gnupg
```
Honestly I don't see the point.
Don't have time to argue about this now, but
1. `make` is a build process;
2. We don't have `[:optional, :run]` deps in core;
3. Making ffmpeg `[:recommended, :run]` is way too heavy-handed for youtube-dl, which is a tiny package;
4. `brew info` does not replace upstream documentation.
@ilovezfs youtube-dl optionally depends on FFmpeg/Libav (just the `ffmpeg`/`avconv` executables) to merge downloaded audio & video streams. If neither is available and audio & video are separate, there's no crash — you just get separate files, unmerged. This is certainly not right.