Move the dependencies to a CDN

[BearishSun]

Currently the binary dependencies and data file dependencies are being hosted on a single server, which is nice because it's low cost. But users have reported weak connectivity to it around the world, with cmake build step failing because of a failed download.

Binary dependencies should be moved to a content delivery network. Quick search reveals DigitalOcean Spaces seems to provide decent bandwidth for the price (especially compared to AWS S3 + CloudFront which is much more expensive).