octave.withPackages: fix null reference on darwin (#447122)

pkgs/development/interpreters/octave/build-env.nix

···
 let
   packages = computeRequiredOctavePackages extraLibs;
 
+  # glibcLocalesUtf8 is null on darwin
+  localeArchiveArgs = lib.optionalString (glibcLocalesUtf8 != null) ''
+    --set LOCALE_ARCHIVE "${glibcLocalesUtf8}/lib/locale/locale-archive"
+  '';
+
 in
 buildEnv {
   name = "${octave.name}-env";
···
            if [ -x $prg ]; then
               makeWrapper "${octave}/bin/$prg" "$out/bin/$prg" \
                           --set OCTAVE_SITE_INITFILE "$out/share/octave/site/m/startup/octaverc" \
-                          --set LOCALE_ARCHIVE "${glibcLocalesUtf8}/lib/locale/locale-archive"
+                          ${localeArchiveArgs}
            fi
        done
        cd $out
···
   ''
   + postBuild;
 
-  inherit (octave) meta;
+  inherit (octave) meta version;
 
-  passthru = octave.passthru // {
+  passthru = (removeAttrs octave.passthru [ "tests" ]) // {
     interpreter = "$out/bin/octave";
     inherit octave;
     env = stdenv.mkDerivation {

pkgs/development/interpreters/octave/default.nix

···
   ncurses,
   perl,
   flex,
+  testers,
   texinfo,
   qhull,
   libsndfile,
···
     withPackages = import ./with-packages.nix { inherit buildEnv octavePackages; };
     pkgs = octavePackages;
     interpreter = "${finalAttrs.finalPackage}/bin/octave";
+    tests = {
+      wrapper = testers.testVersion {
+        package = finalAttrs.finalPackage.withPackages (ps: [ ps.doctest ]);
+        command = "octave --version";
+      };
+    };
   };
 
   meta = {