Fixes native builds on ARM
`HOST_ARCH=arm64 ./make.sh minimal` builds vmlinuz and initrd for arm64 on arm64 (sourcing .docker-env.arm64 in the process) `ARCH=arm ./make.sh rootfs` builds rootfs.tar.gz for arm on your current docker environment
Currently, for amd64 (the default) and arm. Run `dapper make ARCH=arm rootfs` to build rootfs.tar.gz for arm.