added modplug to macosx

[daschuer]

No description provided.

[Be-ing]

Build failed:

scripts/macosx/build_environment.sh: line 131: /Users/mixxx/bs-2.2-mac-prs/amd64/scripts/macosx/build_modplug.sh: Permission denied

https://builds.renegadetech.mixxx.org/job/v2.2/job/buildserver-2.2.x-macosx-prs/architecture=amd64,only_buildserver_capable_nodes=buildserver,platform=macosx/47/console

[JosepMaJAZ]

libopenmpt is the successor of libmodplug ( modplug was made opensource many years ago and the development continued as openmpt).
https://lib.openmpt.org/libopenmpt/

It is on debian, here:
https://packages.debian.org/stable/libs/libopenmpt0

there is even a libmodplug compatibility API if we don't move to the new API:
https://packages.debian.org/stable/libs/libopenmpt-modplug1