fix: Copy extra components on darwin

lib/mk-component-set.nix

@@ -143,6 +143,25 @@ let
           fi
         ''
 
+        # Darwin rustlib helper tools live under `lib/rustlib/<target>/bin`
+        # and use `@loader_path/../lib`, so expose rustc's LLVM dylib there.
+        + optionalString (hostPlatform.isDarwin && pname == "rustc") ''
+          if [[ -e "$out/lib/libLLVM.dylib" ]]; then
+            for binDir in "$out"/lib/rustlib/*/bin; do
+              if [[ ! -d "$binDir" ]]; then
+                continue
+              fi
+              if [[ -e "$binDir/rust-lld" || -e "$binDir/rust-objcopy" || -e "$binDir/wasm-component-ld" ]]; then
+                libDir="$(dirname "$binDir")/lib"
+                mkdir -p "$libDir"
+                if [[ ! -e "$libDir/libLLVM.dylib" && ! -L "$libDir/libLLVM.dylib" ]]; then
+                  ln -s ../../../libLLVM.dylib "$libDir/libLLVM.dylib"
+                fi
+              fi
+            done
+          fi
+        ''
+
         # Wrap the shipped `rust-lld` (lld), which is used by default on some targets.
         # Unfortunately there is no hook to conveniently wrap CC tools inside
         # derivation and `wrapBintools` is designed for wrapping a standalone

tests/default.nix

@@ -48,6 +48,7 @@ let
     date = "2026-01-10";
     version = "1.93.0-beta.6-2026-01-10";
   };
+  sharedLlvmNightly = "2026-06-02";
 
 in
 # Check only tier 1 targets.
@@ -236,4 +237,15 @@ optionalAttrs
     targets = [ "x86_64-apple-darwin" ];
     targetExtensions = [ "rust-docs" ];
   };
+  aarch64-darwin-rustlib-tools-shared-llvm = pkgs.runCommand "aarch64-darwin-rustlib-tools-shared-llvm" { } ''
+    for rustlib in \
+      "${nightly.${sharedLlvmNightly}.rustc}/lib/rustlib/${rustHostPlatform}" \
+      "${nightly.${sharedLlvmNightly}.default}/lib/rustlib/${rustHostPlatform}"
+    do
+      "$rustlib/bin/rust-lld" -flavor wasm --version
+      "$rustlib/bin/rust-objcopy" --version
+      "$rustlib/bin/wasm-component-ld" --version
+    done
+    touch "$out"
+  '';
 }