[clang] [clang] constexpr `__builtin_elementwise_{max, min}` (PR #153563)

[Simon Pilgrim via cfe-commits]

RKSimon wrote:

> Is this still needed after #180885?

If we intend to still support `__builtin_elementwise_max` for fp types then yes

https://github.com/llvm/llvm-project/pull/153563