There are a few different Third Party libraries you have to build
Make sure that you compile and build
freetype
assimp
For the assimp build, you will then need to grab the config.h that is generated in ThirdParty/assimp/build/include/assimp and bring it up to the ThirdParty/assimp/include/assimp folder. Just copy and paste it in
You will also need to install SDL2. If you are on windows, that is the most complicated:
Download SDL2 from here https://www.libsdl.org/
Extract the package into a directory
In the CMake GUI, you will need to set the variable SDL2_DIR to the cmake of that extracted folder, wherever that may be
It should generate and build correctly after that point! :)
If you are on windows, you will also need to grab the dll from the lib/x64 folder (SDL2.dll) and copy it into the build folder as well (Until I write something to automatically do this)
You will need to do the same thing with SDL2_mixer, following the same instructions as before, as well as copying the DLL into the build folder