TasksOfOhm has posted a detailed tutorial on building OpenWRT on TL-WA801ND v2 :
After getting some details about the board it was time to create a build environment. In my case this was just about copying one of the VMs I have prepared just for this purpose. The build environment requires a Linux machine whereas it doesn’t really matter which flavour it is. After everything is set on the VM the very first step is to create a user under which the build will be performed. I created a user ‘openwrt‘ for this and switched user to it.