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

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

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 3494c555c93c, which should contain the `__datasizeof` extension.

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