rust: track latest LLVM to simplify version bumps

pkgs/development/compilers/rust/1_89.nix

@@ -20,8 +20,8 @@
   pkgsTargetTarget,
   makeRustPlatform,
   wrapRustcWith,
-  llvmPackages_20,
-  llvm_20,
+  llvmPackages,
+  llvm,
   wrapCCWith,
   overrideCC,
   fetchpatch,
@@ -29,7 +29,7 @@
 let
   llvmSharedFor =
     pkgSet:
-    pkgSet.llvmPackages_20.libllvm.override (
+    pkgSet.llvmPackages.libllvm.override (
       {
         enableSharedLibraries = true;
       }
@@ -37,7 +37,7 @@ let
         # Force LLVM to compile using clang + LLVM libs when targeting pkgsLLVM
         stdenv = pkgSet.stdenv.override {
           allowedRequisites = null;
-          cc = pkgSet.pkgsBuildHost.llvmPackages_20.clangUseLLVM;
+          cc = pkgSet.pkgsBuildHost.llvmPackages.clangUseLLVM;
         };
       }
     );
@@ -51,12 +51,11 @@ import ./default.nix
     llvmSharedForHost = llvmSharedFor pkgsBuildHost;
     llvmSharedForTarget = llvmSharedFor pkgsBuildTarget;
 
+    inherit llvmPackages;
+
     # For use at runtime
     llvmShared = llvmSharedFor pkgsHostTarget;
 
-    # Expose llvmPackages used for rustc from rustc via passthru for LTO in Firefox
-    llvmPackages = llvmPackages_20;
-
     # Note: the version MUST be the same version that we are building. Upstream
     # ensures that each released compiler can compile itself:
     # https://github.com/NixOS/nixpkgs/pull/351028#issuecomment-2438244363
@@ -87,8 +86,8 @@ import ./default.nix
 
   (
     builtins.removeAttrs args [
-      "llvmPackages_20"
-      "llvm_20"
+      "llvmPackages"
+      "llvm"
       "wrapCCWith"
       "overrideCC"
       "pkgsHostTarget"

pkgs/top-level/all-packages.nix

@@ -5526,9 +5526,7 @@ with pkgs;
   wrapRustcWith = { rustc-unwrapped, ... }@args: callPackage ../build-support/rust/rustc-wrapper args;
   wrapRustc = rustc-unwrapped: wrapRustcWith { inherit rustc-unwrapped; };
 
-  rust_1_89 = callPackage ../development/compilers/rust/1_89.nix {
-    llvm_20 = llvmPackages_20.libllvm;
-  };
+  rust_1_89 = callPackage ../development/compilers/rust/1_89.nix { };
   rust = rust_1_89;
 
   mrustc = callPackage ../development/compilers/mrustc { };