To do:
GDExtension is significantly different from GDNative. GDExtension is meant to extend the godot editor while GDNative is meant to allow writing scripts in C++. This means that GDExtension code is loaded and run when starting the editor, while GDNative is loaded and run when starting the game. While it is possible to check whether code is currently running in the editor, features like hot-reload are still missing and will only be added on coming versions of godot.
Requires:
Note: It seems that clearing the build directory is required to successfully run CMake.