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

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> One clumsy outstanding thing is that this should now be some code in a header that clang includes so that instead of the subprocess shell to handle arch=native clang just looks up the information directly.

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

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