anchor.diff:  ARG CONTAINERD_ALT_VERSION_15=v1.5.11
   # containerd v1.4 for integration tests
   ARG CONTAINERD_ALT_VERSION_14=v1.4.13
  -# available targets: buildkitd, buildkitd.oci_only, buildkitd.containerd_only
  +# BUILDKIT_TARGET defines buildkitd worker mode (buildkitd, buildkitd.oci_only, buildkitd.containerd_only)
   ARG BUILDKIT_TARGET=buildkitd
   ARG REGISTRY_VERSION=2.8.0
   ARG ROOTLESSKIT_VERSION=v0.14.6
  
positive.code: # containerd v1.4 for integration tests
  FROM containerd-base as containerd-alt-14
  ARG CONTAINERD_ALT_VERSION_14
  ARG GO111MODULE=off
  RUN --mount=from=containerd-src,src=/usr/src/containerd,readwrite --mount=target=/root/.cache,type=cache \
    git fetch origin \
    && git checkout -q "$CONTAINERD_ALT_VERSION_14" \
  
negative.code: 
  # build buildkitd binary
  FROM buildkit-base AS buildkitd
  # BUILDKITD_TAGS defines additional Go build tags for compiling buildkitd
  ARG BUILDKITD_TAGS
  ARG TARGETPLATFORM
  RUN --mount=target=. --mount=target=/root/.cache,type=cache \
  