alpine aarch64

run with qemu by:

qemu-system-aarch64 \
    -machine virt \
    -cpu cortex-a53 \
    -smp 1 -m 1G \
    -kernel Image.gz \
    -drive if=none,format=raw,file=rootfs.img,id=hd0 -device virtio-blk-device,drive=hd0 \
    -append "root=/dev/vda rw rootfstype=ext4 console=ttyAMA0" \
    -nographic