0.3.24 Linux/Windows releases weren't built on EC2, but was built on 'gitian' virtual machines (lookup trusted build process here for more info, or get in touch with devrandom).
Thanks for your response.
The reason I asked about EC2 is because I couldn't find step-by-step tutorial to build using Gitian (under Win or Linux). Seems like a great idea, but it appears the building steps are spread out across many posts/readmes/webpages so I'm struggling to make sense of it all.