Strange, it worked for a long time, but for some weeks I did not compile Blender. Obviously install_deps is not enough. Should I manually add such definitions somewhere? Or is there a newer SDL lib dev package to install?
My system is kubuntu, 19.10 (Eoan Ermine), based on plasma 5.16.5.
The current recommended method of building on on Linux is to use the precompiled libraries, is there a reason you are using install_deps.sh instead?
Download the libraries (follow the wiki instructions https://wiki.blender.org/wiki/Building_Blender/Linux/Ubuntu), and create a new build using the precompiled libs (either update CMake or remove the build_linux folder). That should solve the any issues with building.