[clang] [amdgpu-arch] Replace use of HSA with reading sysfs directly (PR #116651)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

> Would only work for Linux unfortunately, unless some Windows driver developer out there knows if there's some similar win32 magic.

Windows getting subprocess calls until their driver catches up (or someone points out how to do this) seems fine to me. Linux people get a slightly faster clang, and maybe even one that prints useful error messages while it dies derived from the return code.

https://github.com/llvm/llvm-project/pull/116651