The first thing to note is that they are only supporting 64 bit systems officially. [...] I'm going to assume at first that you are using a 64 bit system and then end with what you need if you are still using a 32 bit system.
He used an EC2 instance to substitute for a local 64 bit machine, but it works all the same. He includes the commands (package changes) to get the machine where it needs to be to perform the HipHop install and how to get the latest HipHop source from github. Most of the install is handled via packages, but you will need to get into the HipHop source a bit and change a few things for this issue. With everything in place you can run a cmake/make on the source and wait for the resulting binary to be created.
He's condensed down this whole process into one script for those that want a simpler solution.