Adapt Dockerfile to GoReleaser

package/Dockerfile

@@ -1,10 +1,28 @@
+ARG BUILD_ENV=docker
+ARG ARCH
+
 FROM registry.suse.com/bci/bci-base:15.5
 RUN zypper -n update && \
     zypper -n install openssh catatonit git-core && \
     zypper -n clean -a
 RUN useradd -u 1000 -U -m gitjob
-COPY bin/gitjob /usr/bin/
-COPY bin/gitcloner /usr/bin
+
+FROM base AS copy_docker
+ONBUILD ARG ARCH
+ONBUILD COPY bin/gitjob /usr/bin/gitjob
+ONBUILD COPY bin/gitcloner /usr/bin/gitcloner
+
+FROM base AS copy_buildx
+ONBUILD ARG TARGETARCH
+ONBUILD COPY bin/gitjob-linux-$TARGETARCH /usr/bin/gitjob
+ONBUILD COPY bin/gitcloner-linux-$TARGETARCH /usr/bin/gitcloner
+
+FROM base AS copy_goreleaser
+ONBUILD ARG ARCH
+ONBUILD COPY gitjob-linux-${ARCH} /usr/bin/gitjob
+ONBUILD COPY gitcloner-linux-${ARCH} /usr/bin/gitcloner
+
+FROM copy_${BUILD_ENV}
 USER 1000
 ENTRYPOINT ["catatonit", "--"]
 CMD ["gitjob"]