This is simple, example firmware that builds against the GreatFET codebase without existing in the GreatFET tree. It's meant to serve as an example of how one might create a "one-off" firmware for the GreatFET Azalea.
External builds traditionally use the GREATFET_PATH
environment variable to point to the GreatFET repository. With
that variable defined, you can build this like you would any other GreatFET firmware.
# Assuming our GreatFET tree is located at ~/greatfet
export GREATFET_PATH=~/greatfet/
# Configure our build...
mkdir build
cd build
cmake ..
# ... build it, and program the result to a GreatFET Azalea in DFU mode.
make -j5 blinky_external-program