apple-sdk_27: init at 27.0

[sempiternal-aurora]

Another year, another macOS SDK, this time for macOS 27. Follows along in a similar vein to #454747 and #347862, but with a few main differences:

• This year, the way to test whether the sdk compiled was with dup3, for some reason only added post macOS 27
• Apple added a new cpu subtype, arm64e.x1, which requires a back port of the initialisation code to old llvm versions so that we can actually package the sdk
  • So far, linking against it hasn't required changing ld64 to support it, and I don't want to do it, so I'm leaving it as it is, and if in future some problem arises where the linker needs to know about arm64e.x1, then use lld.
  • Sadly, this does mean we need to target staging, as we're rebuilding the Darwin stdenv
• It seems that apple has finally settled on a url for the catalog, replacing 27 or 26 with 17 or 16 in any combination in the link here fails to give a catalog: https://swscan.apple.com/content/catalogs/others/index-27-26-15-14-13-12-10.16-10.15-10.14-10.13-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz
• Without the need to also bump the source releases at the same time, this can come out a month earlier
• I changed the way that the sdks are instantiated in the top-level, this trades off having them built with an earlier compiler in the bootstrap stage for removing callPackages into the by-name directory.

Overall, this was a very straightforward process, only made slightly annoying by the fact that I need to rebuild the stdenv. Don't really have much other comments.

Draft for now as I haven't tested on a pre macOS 27 machine to see what the linking test does.

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.
• Follows the automation/AI policy.

[sempiternal-aurora]

Output on macOS 15 of apple-sdk_27-test:

:(

Output of the same test, with (darwinMinVersionHook "27.0") added to the build inputs:

dyld[73571]: Symbol not found: _dup3
  Referenced from: <ED5AEE15-C1FE-3ED1-B51F-21271D8CDAE1> /nix/store/inj6hls68id58ib8abkr4llfv693lc0p-apple-sdk_27-test/bin/apple-sdk_27-test (built for macOS 27.0 which is newer than running OS)
  Expected in:     <9500400E-A2EC-33F9-B76B-9830E022777A> /usr/lib/libSystem.B.dylib
zsh: abort      result/bin/apple-sdk_27-test

[reckenrode]

Thanks for doing this update, especially the LLVM patches! I expect the LLVM needed by Swift 6.3 will also need its own patch, but I’ll take care of that in the Swift 6.3 PR.