Build aarch64 NVIDIA Jetson Nano image in x64 docker container using GitLab runner

I am trying to build a custom NVIDIA Jetson Nano image (aarch64 architecture) inside a Docker container (running Ubuntu 20.04 x64). I skip the NVIDIA tools part because I am stuck on the first part when creating proofs. I am using the following commands:

apt-get update
apt-get install --no-install-recommends -q -y ca-certificates curl dialog apt-utils bzip2 python gdisk binfmt-support qemu qemu-user-static debootstrap
mkdir -p rootfs
qemu-debootstrap --arch=arm64 --variant=minbase --keyring=/usr/share/keyrings/ubuntu-archive-keyring.gpg focal rootfs

I also tried

debootstrap --arch=arm64 --foreign --variant=minbase --keyring=/usr/share/keyrings/ubuntu-archive-keyring.gpg focal rootfs
chroot rootfs qemu-aarch64-static /bin/bash -c '/debootstrap/debootstrap --second-stage'

but I always get the following error when doing this using GitLab CI.

I: Running command: chroot test /debootstrap/debootstrap --second-stage
chroot: failed to run command '/debootstrap/debootstrap': Exec format error
ERROR: Job failed: exit code 1

When I run this locally in WSL or even in a local Docker container, it works.

I also tried Ubuntu 18.04.4 or skipping "custom rootfs" part at all. However, I need emulation part anyway since NVIDIA tools are executing aarch64 binaries anyway.

Installing BSP Debian packages in /builds/richardds/jetson-nano-image/build/rootfs
chroot: failed to run command 'dpkg': Exec format error
ERROR: Job failed: exit code 1

Could you please recommend me how can I fix it or any other working way to create custom aarch64 rootfs in GitLab-CI environment (running Docker containers)?