compiler_types: Identify compiler versions for __builtin_dynamic_object_size

Clarify when __builtin_dynamic_object_size() is available. All our
supported Clang versions support it. GCC 12 and later support it. Link
to documentation for both.

Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250416172016.work.154-kees@kernel.org


Signed-off-by: Kees Cook <kees@kernel.org>