koji, opensp: Some meta fixes

pkgs/tools/package-management/koji/default.nix

···
     rm -rf $out/nix
   '';
 
-  meta.maintainers = [ stdenv.lib.maintainers.mornfall ];
+  meta = {
+    maintainers = [ stdenv.lib.maintainers.mornfall ];
+    platforms = stdenv.lib.platforms.linux;
+  };
 }

pkgs/tools/text/sgml/opensp/compat.nix

···
 
   setupHook = opensp.setupHook;
 
-  meta.description =
-    "Compatibility wrapper for old programs looking for original sp programs";
+  meta = opensp.meta // {
+    description = "Compatibility wrapper for old programs looking for original sp programs";
+  };
 }