[clang] [CUDA/HIP] Externalize __device__ const variables for symbol lookup (PR #177292)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

Isn't this was `extern const` is for https://godbolt.org/z/T8jqbM67j? That's how you do it in C/C++ if you need the actual symbol.

https://github.com/llvm/llvm-project/pull/177292