Unicorn as in the mythical creature, not what VC’s think about.
Like every sentence that has the word “just”, this is at best horribly simplistic but mostly plain wrong. Let’s dive in more detail into this. If you look up simple Makefiles on the Internet, you might find something like this page. It starts with a very simple (but useless) Makefile and eventually improves it to this:
Source: Nibble Stew – a gathering of development thoughts: “A simple makefile” is a unicorn