gnuplot: migrate to wxGTK32

pkgs/tools/graphics/gnuplot/default.nix

···
 , libXpm ? null
 , libXaw ? null
 , aquaterm ? false
-, withWxGTK ? false, wxGTK ? null
+, withWxGTK ? false, wxGTK32, Cocoa
 , fontconfig ? null
 , gnused ? null
 , coreutils ? null
···
     ++ lib.optional withCaca libcaca
     ++ lib.optionals withX [ libX11 libXpm libXt libXaw ]
     ++ lib.optionals withQt [ qtbase qtsvg ]
-    ++ lib.optional withWxGTK wxGTK;
+    ++ lib.optional withWxGTK wxGTK32
+    ++ lib.optional (withWxGTK && stdenv.isDarwin) Cocoa;
 
   postPatch = ''
     # lrelease is in qttools, not in qtbase.

pkgs/top-level/all-packages.nix

···
 
   gnupg-pkcs11-scd = callPackage ../tools/security/gnupg-pkcs11-scd { };
 
-  gnuplot = libsForQt5.callPackage ../tools/graphics/gnuplot { };
+  gnuplot = libsForQt5.callPackage ../tools/graphics/gnuplot {
+    inherit (darwin.apple_sdk.frameworks) Cocoa;
+  };
 
   gnuplot_qt = gnuplot.override { withQt = true; };