Add lv2, serd, sord, sratom, and lilv support to macOS build. #15

[rryan]

No description provided.

[Be-ing]

Cool, thank you. I think you need to write "closes #15", not just "#15" in the commit message for GitHub to automatically close the issue when this is merged.

[Be-ing]

Shouldn't --lv2dir be /Library/Audio/Plug-Ins/LV2 according to the LV2 standard?

[Be-ing]

Does anything need to be specified for the --lv2dir argument?

[rryan]

If you don't set --lvd2dir then this installer script tries to install a bunch of manifest junk to /Library/Audio/Plug-Ins/LV2 on the build VM, so I changed it to $PREFIX//Library/Audio/Plug-Ins/LV2. I don't know what we're supposed to do with these manifests -- does Mixxx need to install them on the user's computer? We don't have an installer on macOS, the user just drops the Mixxx.app bundle into /Applications.

[rryan]

Put another way, we don't want to change the build VM's global state since each environment should be hermetic, so I had this write to $MIXXX_PREFIX/Library/Audio/Plug-Ins/LV2 instead of /Library/Audio/Plug-Ins/LV2.

From what I can tell, this option only affects where files are written -- I grepped for $MIXXX_PREFIX in all of the generated files and it doesn't occur.

[Be-ing]

Oh, I presumed --lv2dir set the default plugin search path, but it seems I was wrong. It's not clear to me what these manifests do or if they're really necessary. The README in schemas.lv2 says "These are included with LV2 and installed as a bundle to support validation and
more intelligent use of data by hosts."

[Be-ing]

Alright, well I'll merge this now. If there is an issue with macOS builds detecting LV2 plugins, let's keep this in mind.

[rryan]

Cool, thank you. I think you need to write "closes #15", not just "#15" in the commit message for GitHub to automatically close the issue when this is merged.

Yea, I didn't because #15 is about Mac and Windows support so this PR doesn't fully fix it.

[Be-ing]

CI build passed 👍