build upnpc into a static binary

script.sh

`#!/bin/bash

# This script creates a Dockerfile in the current directory using a heredoc,
# then builds a Docker image to compile a static 'upnpc' binary from the official Git repository,
# and finally exports the binary to a local './output' directory.

# Create the Dockerfile using a heredoc
cat <<EOF > Dockerfile
FROM debian:bookworm AS builder

# Step 1: Install build tools and git.
RUN apt-get update && apt-get install -y build-essential git

# Step 2: Clone the official miniupnp repository.
RUN git clone https://github.com/miniupnp/miniupnp.git /build

WORKDIR /build/miniupnpc

# Step 3: Compile only the static binary.
# We explicitly call the 'build/upnpc-static' target to avoid building the shared library.
RUN make LDFLAGS=-static build/upnpc-static

FROM scratch AS exporter
# Copy only the compiled static binary from the builder stage and rename it to 'upnpc'.
# The compiled binary is located in the 'build' subdirectory.
COPY --from=builder /build/miniupnpc/build/upnpc-static /upnpc
EOF

# Build the Docker image and export the final binary to the './output' directory
echo "Dockerfile created. Starting Docker build..."
docker build --platform=linux/amd64 --output type=local,dest=./output -t static-miniupnpc-builder .

# Clean up the Dockerfile
rm Dockerfile

echo "Build complete. The static 'upnpc' binary is in the './output' directory."
`