[clang] [clang] constexpr built-in elementwise add_sat function. (PR #119082)

[via cfe-commits]

================
@@ -414,6 +414,7 @@ Non-comprehensive list of changes in this release
 - ``__builtin_reduce_or`` and ``__builtin_reduce_xor`` functions can now be used in constant expressions.
 - ``__builtin_elementwise_popcount`` function can now be used in constant expressions.
 - ``__builtin_elementwise_bitreverse`` function can now be used in constant expressions.
+- ``__builtin_elementwise_add_sat`` function can now be used in constant expressions.
----------------
cor3ntin wrote:

Can we merge all of these?
"The following builtins can now be used in constant expressions < nested bulleted list>"

https://github.com/llvm/llvm-project/pull/119082