Rebuilding chromium with new logo and name

I have been trying to develop chromium using the ungoogled chromium windows.

github.com/ungoogled-software/ungoogled-chromium-windows

The project uses a build.py file which sets up everything I built the project successfully and changed the logos and the name of chrome using StackOverflow answers. However, I am stuck on how to build it again so that I can get the browser with custom name and logo? If I try to run build.py, it fails because of the already existing src folder. If I try to run the ninja command from build.py directly, it fails. So I am stuck at this point.