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

[Juan Manuel Martinez Caamaño via cfe-commits]

jmmartinez wrote:

When we compile on the device side we pass `-fvisibility=hidden`, right? Is the symbol still visible for the lookup in this case?

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