Beef up support for multiple env templates.

[amjames]

#19 Adds a secondary env file for a free threading build.

It would probably make sense for the environment name customization features to also do an optional search for a similarly named .yaml file when torch-env.sh is run.

[rec]

Which possible customization features do we have, out of curiosity?

By my count, six:

• Free threaded
• MacOS
• Distributed
• TORCH_CUDA_ARCH_LIST
• Debug vs Release vs RelWithDebInfo
• USE_CUDA

Free threaded and MacOS are different from all the others, because of the separate .yml, but now what about free-threaded MacOS?

[amjames]

I don't know about FT + MacOS, Im not sure if it is something we need to worry about proactively we can add it if and when we need it.

Some of these could (probably should) have their own environment files too, if you are not going to build with CUDA, you are probably not on a system with a GPU, so you probably don't need any of the CUDA dependencies in the environment.