[clang] [AMDGPU] Use the AMDGPUToolChain when targeting C/C++ directly (PR #99687)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

So the main reason I want this is so that I don't need to keep passing `-nogpulib` because targeting plain C/C++ should not require the ROCm device libs.

https://github.com/llvm/llvm-project/pull/99687