[flang] [compiler-rt] [libc] [libcxx] [clang-tools-extra] [llvm] [clang] [libc++] Implement LWG3940: std::expected<void, E>::value() also needs E to be copy constructible (PR #71819)

[via llvm-commits]

PragmaTwice wrote:

> > The CI finally passed now : )
> 
> Great. A few minor comment and then it LGTM. I'll leave the final approval to @huixie90

Thank you! Comments has been addressed now.

https://github.com/llvm/llvm-project/pull/71819