Add docker cli to the runner image. (#2425)

images/Dockerfile

@@ -3,6 +3,7 @@ FROM mcr.microsoft.com/dotnet/runtime-deps:6.0 as build
 ARG RUNNER_VERSION
 ARG RUNNER_ARCH="x64"
 ARG RUNNER_CONTAINER_HOOKS_VERSION=0.2.0
+ARG DOCKER_VERSION=20.10.23
 
 RUN apt update -y && apt install curl unzip -y
 
@@ -15,6 +16,12 @@ RUN curl -f -L -o runner-container-hooks.zip https://github.com/actions/runner-c
     && unzip ./runner-container-hooks.zip -d ./k8s \
     && rm runner-container-hooks.zip
 
+RUN export DOCKER_ARCH=x86_64 \
+    && if [ "$RUNNER_ARCH" = "arm64" ]; then export DOCKER_ARCH=aarch64 ; fi \
+    && curl -fLo docker.tgz https://download.docker.com/linux/static/stable/${DOCKER_ARCH}/docker-${DOCKER_VERSION}.tgz \
+    && tar zxvf docker.tgz \
+    && rm -rf docker.tgz
+
 FROM mcr.microsoft.com/dotnet/runtime-deps:6.0
 
 ENV RUNNER_ALLOW_RUNASROOT=1
@@ -23,3 +30,5 @@ ENV ACTIONS_RUNNER_PRINT_LOG_TO_STDOUT=1
 
 WORKDIR /actions-runner
 COPY --from=build /actions-runner .
+
+RUN install -o root -g root -m 755 docker/* /usr/bin/ && rm -rf docker