I don't think you can take the merit away from the build system author so easily. As the article states and the manual mentions, a clever build system based on make, without using recursive Makefiles, took 10 seconds to start compiling after modifying a file, and the new build system takes less than one second, on the same Linux system. No doubt the OS has many things to say regarding process start time, filesystem access, etc. But the big differences come from the build system, entirely in the userspace side.