build(docker): optimize docker image layers

use COPY --chown instead of chown in Dockerfile to reduce the number of layers

deploy/docker/Dockerfile

@@ -26,6 +26,7 @@ WORKDIR /emqx/
 RUN mkdir -p /emqx-rel/emqx && \
     if [ -f "/${PROFILE}.tar.gz" ]; then \
       tar zxf "/${PROFILE}.tar.gz" -C /emqx-rel/emqx; \
+      find /emqx-rel/emqx -name 'swagger*.js.map' -exec rm {} +; \
     else \
       if [ -f rebar-git-cache.tar ]; then \
         mkdir .cache && \
@@ -37,6 +38,7 @@ RUN mkdir -p /emqx-rel/emqx && \
       git config --global --add safe.directory '*' && \
       make ${PROFILE}-tgz && \
       tar zxf _packages/${PROFILE}/*.tar.gz -C /emqx-rel/emqx; \
+      find /emqx-rel/emqx -name 'swagger*.js.map' -exec rm {} +; \
     fi
 
 FROM $RUN_FROM
@@ -46,22 +48,19 @@ ARG EXTRA_DEPS=''
 ENV LC_ALL=C.UTF-8
 ENV LANG=C.UTF-8
 
-COPY deploy/docker/docker-entrypoint.sh /usr/bin/
-COPY --from=builder /emqx-rel /opt/
-
-WORKDIR /opt/emqx
-
 RUN set -eu; \
     apt-get update; \
     apt-get install -y --no-install-recommends ca-certificates procps $(echo "${EXTRA_DEPS}" | tr ',' ' '); \
-    find /opt/emqx -name 'swagger*.js.map' -exec rm {} +; \
+    rm -rf /var/lib/apt/lists/*; \
     groupadd -r -g 1000 emqx; \
-    useradd -r -m -u 1000 -g emqx emqx; \
+    useradd -r -m -u 1000 -g emqx emqx
-    chgrp -Rf emqx /opt/emqx; \
+
-    chmod -Rf g+w /opt/emqx; \
+COPY deploy/docker/docker-entrypoint.sh /usr/bin/
-    chown -Rf emqx /opt/emqx; \
+COPY --from=builder --chown=emqx:emqx /emqx-rel /opt/
-    ln -s /opt/emqx/bin/* /usr/local/bin/; \
+
-    rm -rf /var/lib/apt/lists/*
+RUN ln -s /opt/emqx/bin/* /usr/local/bin/
+
+WORKDIR /opt/emqx
 
 USER emqx