llvmPackages_git: move everything to common

[RossComputerGuy]

Description of changes

This PR moves all packages from pkgs/development/compilers/llvm/git into pkgs/development/compilers/llvm/common. This makes the upgrade process simpler for git and packaging a new LLVM version will be more straight forward. We'll also have less redundant files.

Things done

Progress:

• lld
• clang
• compiler-rt
• libcxx
• libunwind
• llvm
• openmp

• 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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Add a 👍 reaction to pull requests you find important.

[wegank]

It looks like there are already a few LLVM subprojects moved to common. If you wish, you can open separate PRs for them to speed up reviews and merges.

[RossComputerGuy]

It looks like there are already a few LLVM subprojects moved to common. If you wish, you can open separate PRs for them to speed up reviews and merges.

Good idea.

[RossComputerGuy]

lld has been split into #303438, going to keep this PR open until I finish splitting everything else.