> It’s insane. 45 minutes to build debug from scratch. Linking is super slow even in debug and that’s without LTO.

How much memory do you have, and do you have swap turned on?

I have 32GB of RAM, and it barely manages to build release if I shut down everything else on the system that uses RAM. 64GB would be better. If you have 32GB or less and you have swap on, the performance might be mostly because you're spending a lot of time swapping. And that's for release; debug on a repo that size may spend a lot of time and memory linking debug info.