Make openwrt build from source

Step into source folder

cd ~/openwrt    
mkdir -p logs    

Step into git branch

git checkout lede-17.01.04-tl-mr3420-v1-usbmount    

Update Files

git pull  
./scripts/feeds update -a    
./scripts/feeds install -a    

Change config file

wget https://downloads.lede-project.org/snapshots/targets/ar71xx/tiny/config.seed -O config.tiny.seed   
wget https://downloads.lede-project.org/releases/17.01.4/targets/ar71xx/generic/config.seed 
cp config.seed .config   
#cp lede-17.01.4-ar71xx-generic-tl-mr3420-v1-usbmount.diffconfig .config        
make defconfig    
make oldconfig    
make menuconfig    

Compile it

# make dirclean # deletes contents of the directories /bin and /build_dir and additionally /staging_dir and /toolchain and /logs. 
make download  
rm logs/build.log     
FORCE_UNSAFE_CONFIGURE=1 ionice -c 3 nice -n 19 make -j 5 V=s 2>&1 | tee logs/build.log | grep -i -E "^make.*(error|[12345]...Entering dir)"    
ls ~/openwrt/bin/targets/ar71xx/generic/ -la

Save config and results for later use f2fs filesystem

cp .config lede-17.01.4-ar71xx-generic-tl-mr3420-v1-usbmount.config  
scripts/diffconfig.sh > lede-17.01.4-ar71xx-generic-tl-mr3420-v1-usbmount.diffconfig    
mv bin/targets/ar71xx/generic/*.manifest lede-17.01.4-ar71xx-generic-tl-mr3420-v1-usbmount.manifest    
cp ~/openwrt/bin/targets/ar71xx/generic/lede-17.01.4-ar71xx-generic-tl-mr3420-v1-squashfs-sysupgrade.bin lede-17.01.4-ar71xx-generic-tl-mr3420-v1-usbmount-sysupgrade.bin  
cp ~/openwrt/bin/targets/ar71xx/generic/lede-17.01.4-ar71xx-generic-tl-mr3420-v1-squashfs-factory.bin lede-17.01.4-ar71xx-generic-tl-mr3420-v1-usbmount-factory.bin 

Save config and results for later use rootfs filesystem

cp .config lede-17.01.4-ar71xx-generic-tl-mr3420-v1-rootfs.config  
scripts/diffconfig.sh > lede-17.01.4-ar71xx-generic-tl-mr3420-v1-rootfs.diffconfig    
mv bin/targets/ar71xx/generic/*.manifest lede-17.01.4-ar71xx-generic-tl-mr3420-v1-rootfs.manifest    
cp ~/openwrt/bin/targets/ar71xx/generic/lede-17.01.4-ar71xx-generic-device-tl-mr3420-v1-rootfs.tar.gz lede-17.01.4-ar71xx-generic-tl-mr3420-v1-rootfs.tar.gz