python3Packages.rerun-sdk: fix -liconv on darwin

Cf. https://hydra.nixos.org/build/254442092/nixlog/1

pkgs/development/python-modules/rerun-sdk/default.nix

@@ -12,6 +12,7 @@
   typing-extensions,
   pytestCheckHook,
   python,
+  libiconv,
 }:
 
 buildPythonPackage {
@@ -27,6 +28,10 @@ buildPythonPackage {
     rustPlatform.maturinBuildHook
   ];
 
+  buildInputs = [
+    libiconv # No-op on Linux, necessary on Darwin.
+  ];
+
   propagatedBuildInputs = [
     attrs
     numpy