We have a very similar problem [except we have videos that need to sit right next to the code tree] and we have added those video subfolders into .gitignore and use rsync for those instead - simple and effective tool-per-task.

I don't believe in 6GB source trees without binary blobs. Perhaps Windows codebase is that large but I would assume it's hosted in multiple repos and very rarely is built/checked out by individual developers all at once.