[bityard]

Not as basic as you seem to think.

I was brought into a team of 70-ish engineers working across 4-5 products. Big enterprise products written by very bright programmers. But build systems and infrastructure were not their core competency. Their flagship application took 6 hours to build when I was hired. I got it down to 30-45 minutes using a combination of the techniques above and a revamped build infrastructure. When I finally left that position, the build was much more modular, so you could rebuild a small part of it and glue it into a bunch of existing artifacts and have a final product in just a few minutes.