nrf52-keyboard environment structures

SDCC

//it use to build ch554 fireware.Before that,you should install git and make
//https://github.com/Blinkinlabs/ch554_sdcc
sudo apt install sdcc

nrfutil

sudo apt install python3 python3-pip
pip3 install nrfutil //install nrfutil

//it may not work,so you can download it directly
//https://github.com/NordicSemiconductor/pc-nrfutil/releases
- first download 
- rename nrfutil
- move to /usr/bin
- Use chmod to add executable permissions

mergehex

Download from https://www.nordicsemi.com/Products/Development-tools/nrf-command-line-tools/download
find the mergehex file and move it to /usr/bin.
By the way,you should use chmod to add executable permissions

Gcc

wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2
# you must use this version
tar xf gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2
mv gcc-arm-none-eabi-7-2018-q2-update/ /usr/local/