[clang] [Clang] Fix __is_array returning true for zero-sized arrays (PR #86652)

[Jonathan Wakely via cfe-commits]

jwakely wrote:

Last time I checked, neither GCC nor Clang allowed T[0] to match a partial specialization for `is_array<T[N]>` so the extension isn't very well extended :)

https://github.com/llvm/llvm-project/pull/86652