The repository this patch was done from is this one: https://github.com/bitcraze/crazyflie-firmware

And the hash from the exact commit we pulled from:

f4d21213d7ce37d7ed7338fad0f9a94a96cec191

To apply the patch, just write the following commands:

git clone https://github.com/bitcraze/crazyflie-firmware.git
cd crazyflie-firmware
git submodule init && git submodule update
git checkout f4d21213d7ce37d7ed7338fad0f9a94a96cec191
git apply <folder_to_D-FaLL-System_repository>/crazyflie_firmware/firmware_modifications.patch

Now the repository is ready to compile. To do it, first make sure that you have installed the toolchain. To install it:
sudo add-apt-repository ppa:team-gcc-arm-embedded/ppa
sudo apt-get update
sudo apt-get install libnewlib-arm-none-eabi

Then, in the crazyflie-firmware folder where you applied the patch, do:
make PLATFORM=CF2

If everything is successful, you will see something like this:

Now the binary file cf2.bin has been created, and can be directly uploaded to the crazyflie