The Hydra build of the LLVM bump progressed very slowly because the minis were swamped by a couple staging rebuilds, so I focused on the SDK bump.
I rebased the previous work on the LLVM bump and started updating the Apple source releases.
The source releases are what Nixpkgs tries to depend on for macOS builds when possible.
Updating them involves adding to the header lists the releases are checked against when new headers are added, as for CommonCrypto this time around.
Sometimes headers change location in the source tarball, requiring an update to the buildPhase, like for the new libdispatch.
And occasionally headers are removed in new version, in this case we create a package that combines headers from the new and old version so code that relies on these headers still compiles, as happened to libdispatch and xnu.
I looked into building packages against newer SDK frameworks, which came up in this issue.
But I got stuck on the rewriting of dylib paths and didn't see a clear way forward.
Finally with most of the Hydra build for the LLVM bump finished I was able to start looking into fixing the cups build which caused most of the new build failures due to being a common (transitive) dependency, I have a patch but ended up running into failures the hydra builders haven't encountered and am looking into this.
The new Hydra evaluation has started.
I also wrote a tutorial to get people started on recent versions of macOS (soon regardless of CPU), with step-by-step uninstallation instructions to reduce the fear of ending up with a cluttered system or make it easy to start from scratch. This is intended to go into the Nix manual. A nix-darwin setup tutorial would be next.