Finally managed to build the game on ArchLinux.
I had to do the following things:
- change CEGUIBase to CEGUIBase-0 and CEGUIOgreRenderer to CEGUIOgreRenderer-0 in cmake/modules/FindCEGUI.cmake
- add cegui-0/CEGUI to PATH_SUFFIXES line 18 of cmake/modules/FindCEGUI.cmake
- after cmake, use cmake-gui to remove the ending CEGUI in CEGUI_INCLUDE_DIR (this might be a bug of the FindCEGUI.cmake which search CEGUI.h instead of CEGUI/CEGUI.h)
The first two things are because ArchLinux CEGUI packages are weird and add this "-0" suffix because it’s the major version number.