Upstream has decided to now ship the ffmpeg-mux executable as a binary
in /usr/bin. In order to keep the -plugins package Multiarch: Same, we
still need to ship it in /usr/lib/x86_64, although we now use the new
name to not diverge too much from upstream.
To build the debian package, it's recommended to use git-buildpackage.
It's assumed the debian files is in the "debian" branch, and the obs
upstream source is in the "master" branch. Override if necessary.