# Download and extract the binary to the output directory.
    echo "Downloading ${SIDECAR}: $1 to $2"
    time ${DOWNLOAD_COMMAND} --header "${AUTH_HEADER:-}" "$1" |\
      tar --extract --gzip --strip-components=3 --to-stdout > "$2"
    chmod +x "$2"

    # Make a copy named just "envoy" in the same directory (overwrite if necessary).
    echo "Copying $2 to $(dirname "$2")/${3}"
    cp -f "$2" "$(dirname "$2")/${3}"