libwebp_anim encoder is missing

[marto55555]

Since commit d6c6a37, ffmpeg -encoders shows only libwebp and not libwebp_anim.

Given that for some types of files, libwebp_anim generates better animated webp's than libwebp, would it be possible to reintroduce it in a way that works?

[BtbN]

The anim one got accidentally disabled cause it depends on a sub-library that seemed useless to me, libwebpmux.
Though both encoders call out to the exact same library to do the actual encoding, just one does the muxing natively in ffmpeg, while the other uses libwebpmux.
I would not expect any difference between them whatsoever normally.