After wrestling with creating a nice gulpfile for the past two days (essentially wasting two days), I think this is the right route. My biggest gripe with gulp is that creating reusable pipelines even with lazypipe is unnecessarily difficult and can make debugging build scripts (!) hard.
This one is rather simple but includes steps for building and optimizing JS and CSS. It also has support for different build environments (Gitboard has a Chrome version and a web version).
I used to go with Makefiles maybe two years ago but there's really no point on using anything else other than npm scripts if you already have a Node.js set of tools (therefore an npm manifest).
One great thing about npm scripts is that every time you run a command Node.js will export the binaries path to your $PATH so you don't have to manually add absolute paths.
Can you post an example of one of your makefiles?