use modern cmake

[prudhomm]

this is not a good idea to use include_directories, it is preferred to use target_include_directories which way cleaner. it is called modern cmake: see eg here https://cliutils.gitlab.io/modern-cmake/chapters/intro/dodonot.html

I can give a shot at fixing this if you like @berenger-eu

[berenger-eu]

Yes I know, it is on my list since years.... I will try to do it (start now and hope to achieve in the coming weeks).