[clang] [llvm] Make OpenCL an OSType rather than an EnvironmentType. (PR #170297)

[Alexey Bader via llvm-commits]

bader wrote:

> > OpenCL should be neither an operating system or an environment. It's a source language, not a target ABI. I think we used to mishandle HIP and OpenCL differences and I don't think AMD is using this anymore
> 
> There must be some feature to separate GPU code execution environments (e.g. OpenCL and Vulkan). @arsenm, do you have a constructive proposal to separate them?

Ping.

@arsenm, based on your comment I assume this change won't break OpenCL implementation for AMDGPU. 
If you are not happy with the current patch, please, share your ideas on handling SPIR-V differences between OpenCL and Vulkan execution environments.

https://github.com/llvm/llvm-project/pull/170297