llvmPackages_{12,13,14,15,16,17,18,git}: use common llvm

[RossComputerGuy]

Description of changes

Partial split from #299807

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• 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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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.

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[RossComputerGuy]

Just need to fix the Darwin issue, idk why it happens.

[RossComputerGuy]

No more merge conflict

Edit: I was in the wrong branch

[wegank]

Oh, this PR also targets staging, but I think master should be OK?

[RossComputerGuy]

@wegank No, I tried master but I was getting those spooky binutils.override missing errors in pkgs/stdenv/adapters.nix. I was suggested to switch to staging and it fixed my issues.

[wegank]

And another merge conflict here.

[RossComputerGuy]

Fixed the merge conflict