MINIFICPP-1114 - Fix u16 docker build

Signed-off-by: Arpad Boda <aboda@apache.org>

This closes #704

docker/xenial/Dockerfile

@@ -34,7 +34,12 @@ ENV MINIFI_BASE_DIR /opt/minifi
 RUN mkdir -p $MINIFI_BASE_DIR 
 USER $USER
 
+
 RUN apt-get update && apt-get install -y openjdk-8-jdk openjdk-8-source sudo git maven autogen autoconf automake
+RUN apt-get install -y apt-transport-https ca-certificates gnupg software-properties-common wget
+RUN wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | apt-key add -
+RUN apt-add-repository 'deb https://apt.kitware.com/ubuntu/ xenial main' && apt-get update
+RUN apt-get install -y cmake
 
 
 ADD $MINIFI_SOURCE_CODE $MINIFI_BASE_DIR