build: Makefile with cross-builds (linux/termux arm64, armv7), non-root distroless Dockerfile, example config

Dockerfile

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+# syntax=docker/dockerfile:1
+# Pinned Go version, matches go.mod (go 1.25).
+FROM golang:1.25.3-alpine AS build
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+ARG VERSION=docker
+RUN CGO_ENABLED=0 go build -trimpath -ldflags "-s -w -X main.version=${VERSION}" -o /out/openclaw ./cmd/openclaw \
+ && mkdir -p /out/data
+
+FROM gcr.io/distroless/static-debian12:nonroot
+COPY --from=build /out/openclaw /usr/local/bin/openclaw
+COPY --from=build --chown=65532:65532 /out/data /data
+ENV OPENCLAW_DATA_DIR=/data \
+    OPENCLAW_LISTEN=0.0.0.0:8787
+USER 65532:65532
+EXPOSE 8787
+VOLUME ["/data"]
+ENTRYPOINT ["/usr/local/bin/openclaw"]