How to build the GDExtension (using Godot 4.1):
cd godot-cpp
git submodule update --init
scons platform=<platform> -j16
cd ..
scons platform=<platform>Note: -j16 indicates that you CPU can use 16 threads
<platform> can be windows, macos or linux.
Then, open the Godot proyect in demo folder.
To use another version of Godot, read the official Godot documentation on using C++ GDExtensions