anchor.diff:    && ln -s /sbin/iptables-legacy /usr/bin/iptables \
     && xx-go --wrap
   # musl is needed to directly use the registry binary that is built on alpine
  -ENV BUILDKIT_INTEGRATION_CONTAINERD_EXTRA="containerd-1.3=/opt/containerd-alt/bin"
  +ENV BUILDKIT_INTEGRATION_CONTAINERD_EXTRA="containerd-1.4=/opt/containerd-alt/bin"
   ENV BUILDKIT_INTEGRATION_SNAPSHOTTER=stargz
   ENV CGO_ENABLED=0
   COPY --from=stargz-snapshotter /out/* /usr/bin/
  
positive.code: # syntax = docker/dockerfile:1.2
  
  ARG RUNC_VERSION=v1.0.0-rc93
  ARG CONTAINERD_VERSION=v1.4.3
  # containerd v1.3 for integration tests
  ARG CONTAINERD_ALT_VERSION=v1.3.7
  # available targets: buildkitd, buildkitd.oci_only, buildkitd.containerd_only
  ARG BUILDKIT_TARGET=buildkitd
  ARG REGISTRY_VERSION=2.7.1
  
negative.code:   && make bin/ctr \
    && mv bin /out
  
  # containerd v1.4 for integration tests
  FROM containerd-base as containerd-alt
  ARG CONTAINERD_ALT_VERSION
  RUN --mount=from=containerd-src,src=/usr/src/containerd,readwrite --mount=target=/root/.cache,type=cache \
  