Help compiling HandBrake from source

[Baenwort]

I'm trying to solve an error I get when encoding recorded broadcast videos. I'm using Handbrake to do this and per HandBrake support I need to compile instead of using pkg to install HandBrake on BSD derivatives. https://forum.handbrake.fr/viewtopic.php?f=10&t=39774&sid=8635a24171ee20fadaee84d7d3227a64

So I'm trying to follow the directions to compile HandBrake from source from the official guide. https://handbrake.fr/docs/en/latest/developer/build-bsd.html However, when I reach the step that has me run

Code:

./configure --launch-jobs=$(sysctl -n hw.ncpu) --launch --disable-gtk

it throws an invalid variable error. The step is for plain FreeBSD which makes it likely the problem lies in that I need to convert it for FreeNAS jail use.

This is however beyond my skills so I've come asking here for help.