Add Containerfile/Dockerfile (debian:sid installation command)

[emanuelb]

Below Containerfile was used to build this repo using debian:sid-slim by running command: podman build --rm -t darwinsdk .

FROM docker.io/debian:sid-slim
ENV DEBIAN_FRONTEND=noninteractive

COPY . /darwinsdk/
WORKDIR /darwinsdk/

RUN set -ex; \
    apt-get update; \
    apt-get install --yes --no-install-recommends \
        clang libssl-dev dpkg-dev fakeroot debhelper llvm-dev uuid-dev libblocksruntime-dev libc6-dev-i386 gcc-multilib build-essential flex tcsh bison automake autogen libtool libdb-dev; \
    echo 'deb http://deb.debian.org/debian stretch main' >> /etc/apt/sources.list; \
    apt-get update; \
    apt-get install --yes --no-install-recommends clang-4.0;

RUN dpkg-buildpackage -us -uc; \
    dpkg -i ../darwin-sdk*.deb;