lean4, leanPackages.lean4: fix darwin build by adding libtool

Lake 4.30.0 uses libtool -static on macOS for static library targets
instead of ar.
https://github.com/leanprover/lean4/blob/d024af099ca4bf2c86f649261ebf59565dc8c622/src/lake/Lake/Build/Library.lean#L87-L95

See Hydra Build No. 330752454, lean4.aarch64-darwin (June 4, 2026),
https://hydra.nixos.org/build/330752454; Hydra Build No. 330752481,
leanPackages.lean4.aarch64-darwin (June 4, 2026),
https://hydra.nixos.org/build/330752481.

Breakage introduced in
https://github.com/NixOS/nixpkgs/pull/526718/commits/a26b66330f6fa572e7005ee2a1eb031093456e6e

pkgs/by-name/le/lean4/package.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   cmake,
+  cctools,
   fetchFromGitHub,
   git,
   gmp,
@@ -67,7 +68,8 @@ stdenv.mkDerivation (finalAttrs: {
     pkg-config
     makeWrapper
     leangz # Provides leantar
-  ];
+  ]
+  ++ lib.optionals stdenv.hostPlatform.isDarwin [ cctools.libtool ];
 
   buildInputs = [
     gmp

pkgs/development/lean-modules/lean4/default.nix

@@ -4,6 +4,7 @@
   stdenv,
   symlinkJoin,
   cmake,
+  cctools,
   fetchFromGitHub,
   git,
   gmp,
@@ -75,7 +76,8 @@ let
       cmake
       leangz
       pkg-config
-    ];
+    ]
+    ++ lib.optionals stdenv.hostPlatform.isDarwin [ cctools.libtool ];
 
     buildInputs = [
       gmp