libcxx update

[glebm]

It'd be great if libcxx could be updated to a more recent upstream. The latest release is 3 years old at this point and it'd be great to have some of the new features (especially for cross-platform projects like DevilutionX, diasurgical/devilutionX#6929).

Posting the feature request here because https://github.com/OpenOrbis/llvm-project does not allow posting Issues.

[seuros]

@glebm , do you want to pair on this ? I have some progress locally.

[glebm]

@seuros I don't know much about PS4 (I'm not the author of the DevilutionX PS4 port), so I'm not sure if I'll be of much help here.
I do know C++ fairly well.

[kiwidoggie]

If you are willing to help, we are in process of moving to a completely new version of the toolchain using BSD libc + latest LLVM. It's currently a private project with many smaller things needed to be completed

[glebm]

I'm happy to test DevilutionX with it on CI once a Docker image is available. 👍
DevilutionX is a C++17 codebase (using a bit of C++20 where available), if it works then it is likely a lot of other things will do too.