Add CI for earliest supported macOS version #540
Description
We either need a macOS 13 runner, or a way to have Metal behave as if it were running an older macOS so we don't introduce failures on older macOS versions when introducing newer Metal features.
I tried option 2 in https://github.com/JuliaGPU/Metal.jl/tree/emulate_old but I can still use logging even though the @device_code_llvm reports macos v13.0.0 and metal v3.0 so I assume there's something missing for compilation to actually fail.
Originally posted by @christiangnrd in #418 (comment)