[clang] [Clang/AMDGPU] Allow zero sized arrays in HIP device code (PR #195716)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

Since this changes HIP device code to accept zero-sized arrays, can we keep a positive SemaHIP test for the new behavior instead of only deleting the old negative test? It would be useful to cover a normal device local array, a templated array, `__host__ __device__`, and `__shared__ T x[0]` so this does not regress later.

https://github.com/llvm/llvm-project/pull/195716