openscad: don't use versionCheckHook on darwin

Unsure why, but this produces no output when running inside a Nix build,
even though the produced binary works fine, and replicating the same
command that versionCheckHook uses outside the build works fine.

pkgs/by-name/op/openscad/package.nix

@@ -120,8 +120,9 @@ stdenv.mkDerivation (finalAttrs: {
     libsForQt5.qmake
     libsForQt5.wrapQtAppsHook
     wrapGAppsHook3
-    versionCheckHook
-  ];
+  ]
+  # versionCheckHook doesn't detect any output on darwin, even though the binary works.
+  ++ lib.optional (!stdenv.hostPlatform.isDarwin) versionCheckHook;
 
   buildInputs = [
     eigen