Switch Fleet Docker agent image to bci-nano

Add tini to the fleet-agent image and use it as entrypoint
for stable PID 1 behavior on bci-nano.

Author: thardeck

charts/fleet-agent/templates/deployment.yaml

@@ -48,7 +48,7 @@ spec:
         {{- end }}
         image: '{{ template "system_default_registry" . }}{{.Values.image.repository}}:{{.Values.image.tag}}'
         name: fleet-agent
-        command:
+        args:
         - fleetagent
         {{- if .Values.debug }}
         - --debug

package/Dockerfile.agent

@@ -1,9 +1,29 @@
 ARG BUILD_ENV=docker
+ARG BUILDPLATFORM
 ARG TARGETPLATFORM
 ARG TARGETARCH
 ARG ARCH=${TARGETARCH}
 
-FROM --platform=linux/${ARCH} registry.suse.com/bci/bci-busybox:16.0 AS base
+# renovate: datasource=github-release-attachments depName=krallin/tini
+ARG TINI_VERSION=v0.19.0
+# renovate: datasource=github-release-attachments depName=krallin/tini digestVersion=v0.19.0
+ARG TINI_SUM_amd64=c5b0666b4cb676901f90dfcb37106783c5fe2077b04590973b885950611b30ee
+# renovate: datasource=github-release-attachments depName=krallin/tini digestVersion=v0.19.0
+ARG TINI_SUM_arm64=eae1d3aa50c48fb23b8cbdf4e369d0910dfc538566bfd09df89a774aa84a48b9
+
+# Download tini binaries on the native build platform to avoid cross-build networking issues.
+FROM --platform=$BUILDPLATFORM registry.suse.com/bci/bci-busybox:16.0 AS tini-downloader
+ARG TINI_VERSION TINI_SUM_amd64 TINI_SUM_arm64
+RUN set -eux; \
+	wget -qO /tini-amd64 "https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini-static-amd64"; \
+	echo "${TINI_SUM_amd64}  /tini-amd64" | sha256sum -c -; \
+	wget -qO /tini-arm64 "https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini-static-arm64"; \
+	echo "${TINI_SUM_arm64}  /tini-arm64" | sha256sum -c -; \
+	chmod 0755 /tini-amd64 /tini-arm64
+
+FROM --platform=linux/${ARCH} registry.suse.com/bci/bci-nano:16.0 AS base
+ARG ARCH
+COPY --from=tini-downloader /tini-${ARCH} /usr/bin/tini
 
 FROM base AS copy_docker
 ONBUILD ARG ARCH
@@ -19,4 +39,5 @@ COPY ${TARGETPLATFORM}/fleetagent-linux-* /usr/bin/fleetagent
 
 FROM copy_${BUILD_ENV}
 USER 1000
+ENTRYPOINT ["tini", "--"]
 CMD ["fleetagent"]