[libcxx-commits] [libcxx] [libc++] Use __datasizeof for __libcpp_datasizeof if available (PR #72104)

[Mark de Wever via libcxx-commits]

mordante wrote:

> This LGTM once you re-upload against `main`, which will cause the CI to execute again against the GH Actions jobs. Like we checked just now, those seem to be running Clang from `main` at commit [3494c55](https://github.com/llvm/llvm-project/commit/3494c555c93c5f5cf5c36a84a819b80a4d922a82), which should contain the `__datasizeof` extension.

This resolves my concern. I wanted to be sure the code worked properly with Clang having that feature available.

https://github.com/llvm/llvm-project/pull/72104