Add standard stage runner to base image

images/base/Dockerfile

@@ -7,3 +7,5 @@ RUN \
     apt-get -y dist-upgrade && \
     apt-get -y install build-essential yasm nasm pkg-config git curl wget cmake unzip subversion autoconf automake libtool cmake clang texinfo texi2html gperf ragel libc6-dev && \
     apt-get -y clean
+
+ADD run_stage.sh /usr/bin/run_stage

images/base/run_stage.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -xe
+source /stage.sh
+ffbuild_dockerbuild
+rm /stage.sh