OpenSubdiv and magic SwiftPM Shader autogeneration
* We do some SwiftPM jiujitsu to automatically inject the
autogenerated Swift header source.
* The magic here is the basis for autogenerated shader code, at
least until SwiftPM irons out more tooling around Swift -> C++.
* Check out how we call our GPUShaders Swift Implementation here:
https://github.com/wabiverse/MetaverseKit/blob/main/Sources/GPUShaders/GPUShaders.swift#L26
directly from CXX, here:
https://github.com/wabiverse/MetaverseKit/blob/main/Sources/OpenSubdiv/osd/GLComputeEvaluator.cpp#L50