I needed to compile the firmware for the HackRF One because I wanted to use a 26MHz TCXO as external clock instead of the standard 10 MHz clock. While doing so I encountered a problem with YAML. It was installed but "make" returned "No module named yaml". The solution is to install YAML system-wide:

sudo apt install python-yaml

The following commands had to be executed for successful compilation:

sudo apt install gcc-arm-none-eabi python python-yaml
git clone https://github.com/mossmann/hackrf.git
cd hackrf/firmware
git submodule init
git submodule update
cd hackrf_usb
mkdir build
cd build
cmake ..
make
# Install firmware to HackRF
hackrf_spiflash -w hackrf_usb.bin