LO 24.2 C++20 baseline

[Caolán McNamara]

On Mon, 2023-09-25 at 08:30 +0200, Miklos Vajna wrote:
> /home/vmiklos/git/libreoffice/core-
> clang/workdir/UnoApiHeadersTarget/offapi/normal/com/sun/star/util/XCl
> oneable.hpp:8:
> /home/vmiklos/git/libreoffice/core-
> clang/workdir/UnoApiHeadersTarget/udkapi/normal/com/sun/star/uno/XInt
> erface.hpp:32:65: error: invalid application of 'sizeof' to an
> incomplete type 'animcore::(anonymous namespace)::AnimationNode'

I'm guessing that https://gerrit.libreoffice.org/c/core/+/157250 would
workaround this by just extending:

commit 5831d5f03a5ea5b89984574ffe436f38500726da
Date:   Tue Aug 1 15:37:45 2023 +0200

    Don't enable the requires clause for some Xcode Clang

which mentions the same error message, to extend from clang <= 14 to
clang <= 15