message: Ubuntu dockerfile uses required CMake version
  As ISPC now requires CMake 3.13 make sure the docker image has the correct version.
  Additionally update to download from the github release page as it has better download speeds.
diff: @@ -11,9 +11,9 @@ MAINTAINER Dmitry Babokin <dmitry.y.babokin@intel.com>
  RUN apt-get -y update && apt-get install -y wget build-essential vim gcc g++ git subversion python3 m4 bison flex zlib1g-dev ncurses-dev libtinfo-dev libc6-dev-i386 && \
  rm -rf /var/lib/apt/lists/*
  -# Download and install required version of cmake (3.12) for ISPC build
  -RUN wget https://cmake.org/files/v3.12/cmake-3.12.0-Linux-x86_64.sh && mkdir /opt/cmake && sh cmake-3.12.0-Linux-x86_64.sh --prefix=/opt/cmake --skip-license && \
  - ln -s /opt/cmake/bin/cmake /usr/local/bin/cmake && rm cmake-3.12.0-Linux-x86_64.sh
  +# Download and install required version of cmake (3.13) for ISPC build
  +RUN wget https://github.com/Kitware/CMake/releases/download/v3.13.5/cmake-3.13.5-Linux-x86_64.sh && mkdir /opt/cmake && sh cmake-3.13.5-Linux-x86_64.sh --prefix=/opt/cmake --skip-license && \
  + ln -s /opt/cmake/bin/cmake /usr/local/bin/cmake && rm cmake-3.13.5-Linux-x86_64.sh
  # If you are behind a proxy, you need to configure git and svn.
  #RUN git config --global --add http.proxy http://proxy.yourcompany.com:888
  