Add Dockerfile for arm64 cross build

docker/Dockerfile.aarch64

@@ -1,4 +1,4 @@
-FROM debian:stable-slim as builder
+FROM multiarch/debian-debootstrap:arm64-stretch-slim as builder
 
 WORKDIR /root/
 
@@ -7,17 +7,22 @@ RUN apt-get -y --no-install-recommends install build-essential subversion fakero
 
 RUN git clone https://github.com/mikma/lxd-openwrt.git
 
-RUN (cd lxd-openwrt && ./build.sh -v snapshot --type plain)
+RUN (cd lxd-openwrt && ./build.sh -v snapshot -a aarch64 --type plain)
 RUN mkdir rootfs
-RUN tar xzf /root/lxd-openwrt/bin/openwrt-snapshot-x86-64-plain.tar.gz -C rootfs
+RUN tar xzf /root/lxd-openwrt/bin/openwrt-snapshot-armvirt-64-plain.tar.gz -C rootfs
 
+ENV ROOTFS /root/rootfs
+ENV LD_LIBRARY_PATH=$ROOTFS/lib
+RUN mkdir -p $ROOTFS/var/lock
+RUN ln -s $ROOTFS/lib/ld-musl-aarch64.so.1 /lib
+RUN $ROOTFS/bin/opkg -o $ROOTFS update
+RUN $ROOTFS/bin/opkg -o $ROOTFS install luci-ssl
 
 FROM scratch
 
 COPY --from=builder /root/rootfs /
+#COPY --from=builder /usr/bin/qemu-aarch64-static /usr/bin
 
 COPY init.sh /
 
-RUN mkdir -p /var/lock && opkg update && opkg install luci-ssl
-
 ENTRYPOINT ["/init.sh"]