llvm 15, 16: add zstd support

[SaltyKitkat]

Description of changes

Since llvm 16 support using zstd as its compression method, we should also support that.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[rrbutani]

(for anyone following along, this is another attempt at #238266)

[rrbutani]

Thanks for continuing to work on this; a few more things:

• can you change your commit to start with llvm_16 instead of llvm 16? ofborg picks up the former and it's convention
• as mentioned in #238266 LLVM 16+ has a LLVM_USE_STATIC_ZSTD option; given the direction bzip2, zstd: Add enableStatic option #237563 is headed (i.e. potentially having static/dynamic library outputs present with isStatic = false/isStatic = true respectively IIUC) I think it'd be good to add something like this to cmakeFlags:

  ++ lib.optional enableZstd "-DLLVM_USE_STATIC_ZSTD=${toString stdenv.hostPlatform.isStatic}"

• as mentioned, now that we're targeting staging anyways we can apply these changes (minus the LLVM_USE_STATIC_ZSTD bit) to llvmPackages_15 in this PR

[SaltyKitkat]

Is it necessary to mention this change in release note or something like that?

[SaltyKitkat]

Thanks for continuing to work on this; a few more things:

• can you change your commit to start with llvm_16 instead of llvm 16? ofborg picks up the former and it's convention

• as mentioned in #238266 LLVM 16+ has a LLVM_USE_STATIC_ZSTD option; given the direction bzip2, zstd: Add enableStatic option #237563 is headed (i.e. potentially having static/dynamic library outputs present with isStatic = false/isStatic = true respectively IIUC) I think it'd be good to add something like this to cmakeFlags:
  nix ++ lib.optional enableZstd "-DLLVM_USE_STATIC_ZSTD=${toString stdenv.hostPlatform.isStatic}"

• as mentioned, now that we're targeting staging anyways we can apply these changes (minus the LLVM_USE_STATIC_ZSTD bit) to llvmPackages_15 in this PR

Besides, I set CmakeFlags LLVM_PREFER_STATIC_ZSTD in llvm 15 due to this

[rrbutani]

Is it necessary to mention this change in release note or something like that?

I think that's not necessary; this isn't a breaking change and enableZstd is enabled by default (users won't have to do anything to get the feature).

---

Besides, I set CmakeFlags LLVM_PREFER_STATIC_ZSTD in llvm 15 due to this

Ah, I traced LLVM_PREFER_STATIC_ZSTD to llvm/llvm-project@c0b4f24 and assumed it didn't make it into LLVM 15 (it was introduced after 15.x branched) but it turns out that this and the commit changing it to LLVM_USE_STATIC_ZSTD were backported to LLVM 15.

So we can just mirror the change you made to llvmPackages_16 exactly.

[rrbutani]

Looks good! Just one last set of nits.