0ad: fix build by using gcc9Stdenv

pkgs/games/0ad/default.nix

···
-{ wxGTK, newScope }:
-
+{ wxGTK, stdenv, newScope }:
 let
   callPackage = newScope self;
 
   self = {
-    zeroad-unwrapped = callPackage ./game.nix { inherit wxGTK; };
+    zeroad-unwrapped = callPackage ./game.nix { inherit wxGTK stdenv; };
 
-    zeroad-data = callPackage ./data.nix { };
+    zeroad-data = callPackage ./data.nix { inherit stdenv; };
 
     zeroad = callPackage ./wrapper.nix { };
   };
 
-in self
+in
+self

pkgs/top-level/all-packages.nix

···
 
   zeroadPackages = dontRecurseIntoAttrs (callPackage ../games/0ad {
     wxGTK = wxGTK30;
+    stdenv = gcc9Stdenv;
   });
 
   zeroad = zeroadPackages.zeroad;