Revert rootful agent images again (#4683)

Co-authored-by: Robert Kaussow <mail@thegeeklab.de>

docker/Dockerfile.agent.multiarch

@@ -0,0 +1,30 @@
+FROM --platform=$BUILDPLATFORM docker.io/golang:1.23 AS build
+
+RUN groupadd -g 1000 woodpecker && \
+  useradd -u 1000 -g 1000 woodpecker && \
+  mkdir -p /etc/woodpecker && \
+  chown -R woodpecker:woodpecker /etc/woodpecker
+
+WORKDIR /src
+COPY . .
+ARG TARGETOS TARGETARCH CI_COMMIT_SHA CI_COMMIT_TAG CI_COMMIT_BRANCH
+RUN --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=cache,target=/go/pkg \
+    make build-agent
+
+FROM scratch
+ENV GODEBUG=netdns=go
+# Internal setting do NOT change! Signals that woodpecker is running inside a container
+ENV WOODPECKER_IN_CONTAINER=true
+EXPOSE 3000
+
+# copy certs from build image
+COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+# copy agent binary
+COPY --from=build /src/dist/woodpecker-agent /bin/
+COPY --from=build /etc/woodpecker /etc
+COPY --from=build /etc/passwd /etc/passwd
+COPY --from=build /etc/group /etc/group
+
+HEALTHCHECK CMD ["/bin/woodpecker-agent", "ping"]
+ENTRYPOINT ["/bin/woodpecker-agent"]