Add a script to make steam build of wesnoth using docker

utils/dockerbuilds/make_steam_build

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+#!/bin/sh -xe
+
+cd steamrt
+docker build -t steamos-wesnoth .
+docker run -it -v $(pwd)/../../..:/wesnoth -v $(pwd)/../steambuild:/output steamos-wesnoth

utils/dockerbuilds/steamrt/Dockerfile

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+FROM steamrt_scout_amd64
+ENV DEBIAN_FRONTEND=noninteractive
+ARG BOOST_VERSION=1.66.0
+ARG BOOST_VERSION_=1_66_0
+
+RUN apt-get update && apt-get -y dist-upgrade && apt-get install -y scons libicu-dev libreadline-dev
+
+RUN wget --max-redirect 3 https://dl.bintray.com/boostorg/release/${BOOST_VERSION}/source/boost_${BOOST_VERSION_}.tar.gz
+RUN mkdir -p /src/boost && tar zxf boost_${BOOST_VERSION_}.tar.gz -C /src/boost --strip-components=1
+RUN cd /src/boost && ./bootstrap.sh --with-libraries=iostreams,regex,system,filesystem,program_options,random,locale && ./b2 toolset=gcc-5 --layout=system link=static variant=release cxxflags='-fPIE -fstack-protector-strong' define=_FORTIFY_SOURCE=2 install
+
+COPY start.sh /staging/start.sh
+RUN cp /lib/libicu*.so.* /lib/x86_64-linux-gnu/libhistory.so.6 /staging/
+
+ENTRYPOINT mkdir /build && cd /build && scons -j `nproc` ctool=gcc-5 cxxtool=g++-5 boostdir=/usr/local/include boostlibdir=/usr/local/lib extra_flags_config=-lrt -Y /wesnoth && cp /build/wesnoth /output/ && cp /staging/* /output/

utils/dockerbuilds/steamrt/start.sh

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+#!/bin/bash
+GAMEDIR=$(cd "${0%/*}" && echo $PWD)
+cd "$GAMEDIR"
+export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$GAMEDIR/lib64"
+exec ./wesnoth "$@"