Add git to docker container used in build pipeline (aws#365)

Author: awschristou

Dockerfile

@@ -2,6 +2,7 @@ FROM ubuntu:latest
 
 RUN apt-get update && apt-get -y upgrade && apt-get -y install xvfb \
     libgtk-3-0 \
+    git \
     gnupg \
     curl \
     libxss1 \