pythonPackages.pyheck: fix build on darwin

- Add libiconv dependency

pkgs/development/python-modules/pyheck/default.nix

@@ -2,11 +2,13 @@
 , buildPythonPackage
 , cargo
 , fetchFromGitHub
+, libiconv
 , poetry-core
 , pytestCheckHook
 , pythonOlder
 , rustc
 , rustPlatform
+, stdenv
 }:
 
 buildPythonPackage rec {
@@ -39,6 +41,8 @@ buildPythonPackage rec {
     rustPlatform.maturinBuildHook
   ];
 
+  buildInputs = lib.optionals stdenv.isDarwin [ libiconv ];
+
   nativeCheckInputs = [
     pytestCheckHook
   ];