Custom recovery img for Apex.

[dabestharpis]

I am trying to build the clockworkmod recovery image for the LG Apex from this tutorial My Brain Hurts: Porting Clockwork Recovery to New Devices However, I am running into problems.
When I run

build/tools/device/mkvendor.sh device_manufacturer_name device_name /your/path/to/the/boot.img

I get this error

unpackbootimg not found. Is your android build environment set up and have the host tools been built?

I also tried this

make -j4 out/host/linux-x86/bin/unpackbootimg

But I am still getting the error. Any ideas?