Add a Dockerfile for a container capable of building cg-brutaltester

To build the container:
docker build -t cg-brutaltester .
To use it to build cg-brutaltester:
docker run -it --rm -v $PWD:/home/user/work -e MY_UID=$UID cg-brutaltester

Dockerfile

@@ -0,0 +1,49 @@
+FROM debian:stretch
+
+# install debian packages:
+ENV DEBIAN_FRONTEND=noninteractive
+RUN set -x -e; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        default-jdk-headless maven \
+        gosu sudo
+
+# setup sudo
+RUN set -x -e; \
+    echo 'ALL ALL=NOPASSWD:ALL' > /etc/sudoers.d/all; \
+    chmod 0400 /etc/sudoers.d/all;
+
+# download and backup dependencies
+COPY pom.xml /tmp/
+RUN set -x -e; \
+    mkdir -p /tmp/deps; \
+    cp -v /tmp/pom.xml /tmp/deps/; \
+    cd /tmp/deps; \
+    mvn install; \
+    mv $HOME/.m2 /usr/share/cg-brutaltester-m2; \
+    rm -rf /tmp/deps
+
+# default command that builds cg-brutaltester
+CMD set -x -e; \
+    mvn package -o
+
+# setup entrypoint with user UID/GID from host
+RUN set -x -e; \
+    (\
+    echo '#!/bin/bash'; \
+    echo 'MY_UID=${MY_UID:-1000}'; \
+    echo 'set -x -e'; \
+    echo 'useradd -M -u "$MY_UID" -o user'; \
+    echo 'echo export PATH="/usr/local/cargo/bin:$PATH" >> /home/user/.bashrc'; \
+    echo 'cp -R /usr/share/cg-brutaltester-m2 /home/user/.m2'; \
+    echo 'chown -R user:user /home/user'; \
+    echo 'cd /home/user/work'; \
+    echo 'exec gosu user "${@:-/bin/bash}"'; \
+    ) > /usr/local/bin/entrypoint.sh; \
+    chmod a+x /usr/local/bin/entrypoint.sh
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+
+# If your UID is 1000, you can simply run the container as
+# docker run -it --rm -v $PWD:/home/user/work cg-brutaltester
+# otherwise, run it as:
+# docker run -it --rm -v $PWD:/home/user/work -e MY_UID=$UID cg-brutaltester