Ask HN: What build tools does Apple use for large-scale macOS projects?

I'm wondering, for people who are at Apple or have been there:

- What do they use far large compilation projects? Specifically, do they use a parallel/distributed build system, and if so, which system and on which machines does it run?

- What are common build times of large macOS components? I'm thinking: The kernel itself, the entirety of XCode, etc.

- What setups/editors, etc. do developers at Apple use for kernel and driver development, or "very large" bundled applications? Is this also done in XCode, or using a more "traditional" environment? What do they use as an equivalent to Makefiles/build configuration?

Other large valley companies give employees access to some pretty beefy hardware (32+ cores, 128GB+ RAM) for development, sometimes locally, sometimes remotely via a build cluster. I would assume that Apple does the same, yet the only possible setup would be using non-Apple (or non-publicly available) hardware. Does Apple internally use a "hackintosh-like" system for builds & development? Or do they just run a large BSD cluster that's binary compatible with macOS?

Similarly, what hardware and OS powers the iCloud backend?