Many software projects take a long time to compile. Sometimes that’s just due to the sheer amount of code, like in the LLVM project. But often a build is slower than it should be for dumb, fixable reasons.
I’ve had the suspicion that most builds are doing dumb stuff, but I had no way to see it. So I’ve been working on a cross-platform tool to help speed up builds (you can try it, see below).