There's a lot of tricks you can do to optimize build times, and I've tried most of them in my previous game engine. Got ~90kloc recompilation time from 15min to something like a few minutes, although that required rewriting a bunch of code to not use templates. And removing boost. Multiple days' work.
But the point is, that I'd like a language that is fast to compile by default. C seems pretty promising, as doing a full unity build of my 25kloc codebase takes something like 3 seconds. Not sure how much of that is actually compilation, and how much IO. I'm expecting the project to grow to something like 100-200kloc, and hopefully never have to spend time figuring out why the compilation takes too long, and instead use that time to do something productive.
I.e. - use dynamic link libraries
- use create static libraries
- carefully manage your dependencies. i.e. only include what you actually need.
- hot reload game logic (where quick iteration is more important)
- compile cache.
- ssd disk
- fast processor
- and yes, agreed. 100kloc is still small.