[clang] [clang][AMDGPU] Don't define feature macros on host code (PR #83558)

[Pierre van Houtryve via cfe-commits]

Pierre-vh wrote:

> This was the original behavior of my patch, but I reverted it because it broke all the HIP headers that were unintentionally relying on this. Has that been resolved?

Was an issue opened for that? How many headers are affected?

https://github.com/llvm/llvm-project/pull/83558