AWS Codebuild: 3nd attempt to speed up install

Author: Daniel Kroening

buildspec.yml

@@ -4,6 +4,7 @@ phases:
   install:
     commands:
       - echo "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu trusty main" > /etc/apt/sources.list.d/toolchain.list
+      - apt-key net-update
       - apt-get update -y
       - apt-get install -y g++-5 flex bison make git libwww-perl patch ccache
       - apt-get install -y openjdk-7-jdk