Add cmake scripts

[sshockwave]

• Fixes wrong CMAKE_ARGS
• Fixes CMake generator error
• Exposes libonnx (mitigates Build this as libonnx #77) along with CMake configuration scripts
  • ...except on Windows. There seems to be incompatible compile DLL options between the built libprotobuf on conda-forge and onnx, which causes unresolved external symbols. To correctly link libprotobuf we might need to build it locally and use static linking as per here and here. I'm leaving that decision to future works.

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[sshockwave]

@conda-forge-admin, please rerender

[ilya-lavrenov]

BTW, does this change also install ONNX cmake files so users can link against this libonnx.so ?
It would be great to have them, we are one of the users :)

[sshockwave]

Exactly! You can check the files being installed around here

[sshockwave]

The patch needs to be improved to have aligned behavior for Win / Unix. Users should expect cmake interface to be available in all cases

@ilya-lavrenov As mentioned above, attempts have been made on Windows but I couldn't link libprotobuf dynamically. Would appreciate suggestions and opinions!