First you have to download the Allwinner SDK 2.0 with Linux Kernel 3.4 from dl.linux-sunxi.org.
Then you need to setup your environment as explained here
Then Build the kernel, kernel modules and u-boot
cd lichee ./build.sh -psun7i_android
When done, continue with Bulding the android image:
cd ../android4.2 cd device/softwinner/ tar zxfv olinuxino-a20.tgz cd ../../ source build/envsetup.sh lunch #select olinuxino-a20_eng extract-bsp make -j4 pack
At this point you have the same Android 4.2.2 .img like the one which is on our wiki and you can program it to your board with Phoenix Suite!