lcevcdec: fix build on Darwin

lcevcdec's CMake configuration uses libtool on Darwin starting with
4.2.0 [1]. Add it to nativeBuildInputs to fix the build on Darwin.

[1]: https://github.com/v-novaltd/LCEVCdec/blame/a254bd474649e5dcd8182689ac414420bfe8d8c3/cmake/modules/Platform/MACOS.cmake#L37-L40

pkgs/by-name/lc/lcevcdec/package.nix

@@ -1,4 +1,5 @@
 {
+  cctools,
   cmake,
   fetchFromGitHub,
   git,
@@ -46,6 +47,9 @@ stdenv.mkDerivation (finalAttrs: {
     git
     pkg-config
     python3
+  ]
+  ++ lib.optionals stdenv.hostPlatform.isDarwin [
+    cctools.libtool
   ];
 
   buildInputs = [