While tracking down another issue, I updated to the latest version of adwaita-swift, which did unfortunately not compile anymore. I think the culprit was introduced with commit id 19aa17c0ab411c0c4e823f2fb103d55cfc78a25f.
The referenced package (https://github.com/stephencelis/CSQLite) uses .apt to reference a system package/lib. This only works on distros which use apt-get as package manager. In my case, using Manjaro this does not work.
Unfortunately I have no good suggestion on how to resolve this issue. So it's just a FYI ;-).
Cheers, Michael