Unify the Dockerfiles by fleshing out build.sh

Script is written to handle it's own dependencies so it can be used within Docker or on the host system

docker/Dockerfile

@@ -0,0 +1,37 @@
+FROM ubuntu:18.04
+
+RUN \
+    apt-get update -qq && \
+    apt-get install -y \
+# x86_64 / generic packages
+      bash git gosu \
+      cmake make build-essential \
+      wget unzip \
+      python3 python3-pip \ 
+# aarch64 packages
+      libffi-dev libssl-dev python3-dev \ 
+    && rm -rf /var/lib/apt/lists/*;
+
+RUN pip3 install adafruit-nrfutil
+
+# build.sh knows how to compile
+COPY build.sh /opt/
+
+# Lets get each in a separate docker layer for better downloads
+# GCC
+RUN bash -c "source /opt/build.sh; GetGcc;"
+# NrfSdk
+RUN bash -c "source /opt/build.sh; GetNrfSdk;"
+# McuBoot
+RUN bash -c "source /opt/build.sh; GetMcuBoot;"
+
+# Set and arg and use it in the env for power to override at build AND runtime
+ARG USER_ID=33333
+ARG GROUP_ID=33333
+ENV USER_ID $USER_ID
+ENV GROUP_ID $GROUP_ID
+
+ENV SOURCES_DIR /sources
+COPY entrypoint.sh /opt/
+ENTRYPOINT ["/opt/entrypoint.sh"]
+CMD ["/opt/build.sh"]