fix dapper builds
FROM ubuntu:18.04
-RUN apt-get update && apt-get install -y git cmake libgtk-3-dev \
+RUN apt-get update && apt-get install -y g++ git cmake libgtk-3-dev \
libglvnd-dev libglu1-mesa-dev freeglut3-dev libasound2-dev
WORKDIR ${DAPPER_SOURCE:-/source}
-ENV DAPPER_OUTPUT bin
-ENTRYPOINT ["sh", "-c", "cmake . && make -j4"]
+ENV DAPPER_OUTPUT build/bin
+ENTRYPOINT ["sh", "-c", "cd build; cmake .. && make -j4"]
