Does not build against ffmpeg master
This is the same issue as this.
Build errors look like this:
../gegl/operations/external/ff-load.c:143:45: error: 'AVStream' has no member named 'codec'
143 | if (p->video_stream && p->video_stream->codec)
| ^~
../gegl/operations/external/ff-save.c:295:9: error: 'AVStream' has no member named 'codec'
295 | c = st->codec;
| ^~