Вот такая проблема, делаю по этой инструкции https://github.com/SDLash3D/xash3d/blob/master/README.md, потом когда делаешь так:
cmake -DHL_SDK_DIR=/opt/halflife -DXASH_SDL=yes -DXASH_VGUI=yes -DCMAKE_OSX_ARCHITECTURES=i386 ..
CMake Error at game_launch/CMakeLists.txt:44 (target_link_libraries):
Cannot specify link libraries for target "SDL2" which is not built by this
project.