Trying to generate a serial number

Hi,

I'm on this stage of the vanilla laptop guide. I git cloned MacInfoPkg, entered it's directory, then run ./macserial --model MacBookPro12,1 (which is the macbook model that most closely resembles my lapotp).

The output I got is ./macserial is a directory. And indeed, when I looked into the MacInfoPkg directory, there is no script file named macserial nor is there one in the macserial folder. What did I do wrong and how can I generate a proper serial number?

thanks in advance