I have a nexus 7 flo tablet (with android 5.0.1) and I tried rooting it using twrp. It gave errors such as "can't mount /data" etc . I had to reflash from the source flo image to restore the device. So, I want to root the device by building the AOSP source. If i just build from source and flash the device will it give root access ? How do i proceed ?. Alternatively, if i just modify the kernel a bit and then load it, will it give me root access ?