Enable linux and mac build in workflow

[stekyne]

• Added linux build to CI and updated cmake
• Added macos build to CI and updated cmake
• Cleaned up windows build to work with most packages
• Building 6x and 7x versions of plugins as per folder changes by @vlazzarini
• Installer for Windows is working still but nothing written for 7x, Mac or Linux
• Fluidsynth is disabled due to VCPKG issue [fluidsynth] build failure with static microsoft/vcpkg#36139
• Websocket vcpkg doesn't seem to work correctly but will address that in Websocket build is not working with VCPKG #26
• FLTK build disabled for Linux FLTK opcodes not building for Linux with VCPKG #27

[stekyne]

@vlazzarini I think this is good enough to merge after this long time and lot of changes. Let me know what you think

[vlazzarini]

Just wondering. I see the csound headers directory in both 6.x and 7.x. Is there a mechanism to keep them in sync with the latest versions? It's not a problem so much for 6.x, which is not going to change, but for 7.x for instance we may update things without breaking ABI and opcodes may depend on it.

I guess before we were depending on FindCsound.cmake. One thing we could do is just grab the sources for Csound from git, build and install a simple no-dependencies copy so that we have the public headers as required. But maybe you have this solved?

[stekyne]

@vlazzarini You're right. I had tried to think of more sustainable mechanisms, such as adding Csound to chocolatey and installing that before running the build. That way the FindCsound.cmake would work on windows. On Linux and Mac, we'd just use the normal package managers and the same FindCsound.cmake method. This was quite slow though and not always working for some reason. I'm also not sure does it work with multiple versions of Csound installed? I figured that the APIs are not changing much or at least, not enough to break the plugins here so I just dumped them into the repo to make it more reliable.

We can do another way if you think it's better but it's working for now.

[vlazzarini]

Can we try doing like I'm doing here with libsndfile?

csound/csound#1986

see the macosx vanilla workflow. We could do something similar with Csound here?

Alternatively, could we not do git submodule?

[stekyne]

Some of the headers are compiled during the build so I don't think we can just lift the headers from the repo or use a submodule/subtree. It's also not that great a DX for local dev. I guess installing a build of Csound makes the most sense and the plugin build already looks for the appropriate csound env vars to find the headers but does this actually work having Csound 6 and 7 installed side by side? If not, then we'll have to do something else.

[vlazzarini]

Exactly, the raw headers are incomplete.
We need to run a build, install somewhere and then pull the headers. I suppose we should be ok with separate actions for each version. A simple build is very quick, at least on Mac and Linux, we install locally and then pass the path to CMake.

Another alternative is just to run CMake, and the incomplete headers are created in the include subdir, we can copy from that. We don't need a full build, but we will still need to install libsndfile to get CMake to run correctly, so it's not much of a gain.