Properly handle when warnings are treated as errors

[CasperWA]

A segmentation fault occurs when a SWIG deprecation warning is raised to error level.

For more information, see this comment by @francescalb.

[francescalb]

I don't know how to fix this, but I have made a test and added it to the ci-workflow that reproduces the problem.
It can be found here #1090

[jesper-friis]

This is an issue with SWIG and has nothing to with DLite. See swig/swig#3061 (comment)