Code signing librhino_native.dylib for arm64 or universal build

[fraguada]

@dan-rigdon-bel mentioning you here because I think you might know about this.

Issue: I've recently added a flag to the CMakeLists.txt to generate a universal build of the macOS librhino_native.dylib. Locally, the resulting lib works on an M1 mac with macOS 12.2.1. Without the arm64 ARCH, the test app throws a dll not found exception on the M1.

When this is built with our GitHub Actions workflow, and the resulting nupkg is referenced in the test app, I get this pop up:

What I've tried:

• We already use codesign in the python build. Copying this to the dotnet build results in an error:

1 identity imported.
Signing 'src/build/macos/Release/librhino3dm_native.dylib'
error: The specified item could not be found in the keychain.
Failed to sign 'src/build/macos/Release/librhino3dm_native.dylib'.
Error: Process completed with exit code 1.

• tried building just arm64, without signing, and it results in the pop up above when tested locally.

Can you help me to diagnose this correctly? It seems to me like a codesign issue.

[fraguada]

Thanks to @dan-rigdon-bel for the help with codesigning and notarizing.