gitlab-ci with buildx using

variables:
  DOCKER_DRIVER: overlay2
  DOCKER_HOST: tcp://docker:2375/
  DOCKER_BUILDKIT: 1

build:
  stage: build
  services:
    - name: docker:dind
      command: ["dockerd", "--host=tcp://0.0.0.0:2375"]
      alias: 'docker'
  image: carlallen/docker:buildx
  before_script:
    - docker buildx create --driver=docker-container --name=buildkit-builder --use
    - docker login -u gitlab-ci-token -p $CI_JOB_TOKEN registry.gitlab.com
  script: |
    docker buildx build \
          --cache-from type=registry,ref=$CI_REGISTRY_IMAGE:cache \
          --cache-to type=registry,ref=$CI_REGISTRY_IMAGE:cache \
          --push \
          --tag $CI_REGISTRY_IMAGE:latest \
          .
  only:
    - master

Thank you for the response!

.docker_build_img:
  # The stage must come before the stage in which the step is needed
  stage: build
  image: docker:latest
  services:
    - docker:dind
  before_script:
    - docker version
    - docker info
    - docker buildx create --driver=docker-container --name=buildkit-builder --use
  script:
    - echo -n $CI_JOB_TOKEN | docker login -u gitlab-ci-token --password-stdin $CI_REGISTRY
    - docker pull $IMGNAME:latest || true
    - docker buildx build . --platform linux/arm/v7 -f $DOCKERFILE --cache-from $IMGNAME:latest -t $IMGNAME:$TAG --load
    - docker push $IMGNAME:$TAG

This ended up working for me as well.