[poppler] .gitlab-ci.yml qt5/demos

[Oliver Sander]

>      CI: make the libcpp build use C++23
>      
>      It will help us make sure we don't do things like std::string s = nullptr; (since that is not possible on C++23)

Very nice move!  The std::string s = nullptr pitfall was very easy to fall into.

Best,
Oliver
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 5198 bytes
Desc: S/MIME Cryptographic Signature
URL: <https://lists.freedesktop.org/archives/poppler/attachments/20220331/2f346b6f/attachment.bin>