WORKING_DIRECTORY does not contain Python module glad
https://github.com/Dav1dde/glad/blob/f237a2bfcec0d9b82b90ec9af4af265c40de7183/cmake/CMakeLists.txt#L235-L247

How is this supposed to work? By using "WORKING_DIRECTORY" we are moving to the build directory as the manual says:

> Execute the command with the given current working directory. **If it is a relative path it will be interpreted relative to the build tree directory corresponding to the current source directory.**

https://cmake.org/cmake/help/latest/command/add_custom_command.html

But then we try to execute the glad python module, that though is located in the source directory.