python3Packages.wasmer: fix Darwin build

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

@@ -1,7 +1,9 @@
 { lib
+, stdenv
 , rustPlatform
 , fetchFromGitHub
 , buildPythonPackage
+, libiconv
 }:
 let
   pname = "wasmer";
@@ -26,6 +28,8 @@ in buildPythonPackage rec {
 
   nativeBuildInputs = with rustPlatform; [ cargoSetupHook maturinBuildHook ];
 
+  buildInputs = lib.optionals stdenv.isDarwin [ libiconv ];
+
   buildAndTestSubdir = "packages/api";
 
   doCheck = false;