A good build system and caching. By "a good build system" I mean a hermetic one like Bazel that can be confident of knowing the inputs to each build step so tha

A good build system and caching. By "a good build system" I mean a hermetic one like Bazel that can be confident of knowing the inputs to each build step so that they can be run or not as appropriate. Sometimes you'll touch a core header file and a lot of things will rebuild, but it should still be a lot better.