chocolateDoom: pull upstream fix for -fno-common toolchains

Without the change build fails on -fno-common toolchains like upstream
gcc-10:

    ld: hexen/libhexen.a(g_game.o):/build/source/src/hexen/g_game.c:101:
      multiple definition of `demoextend'; hexen/libhexen.a(mn_menu.o):
        /build/source/src/hexen/mn_menu.c:134: first defined here

pkgs/games/chocolate-doom/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, autoreconfHook, pkg-config, SDL2, SDL2_mixer, SDL2_net, fetchFromGitHub }:
+{ lib, stdenv, autoreconfHook, pkg-config, SDL2, SDL2_mixer, SDL2_net, fetchFromGitHub, fetchpatch }:
 
 stdenv.mkDerivation rec {
   pname = "chocolate-doom";
@@ -11,6 +11,16 @@ stdenv.mkDerivation rec {
     sha256 = "1zlcqhd49c5n8vaahgaqrc2y10z86xng51sbd82xm3rk2dly25jp";
   };
 
+  patches = [
+    # Pull upstream patch to fix builx against gcc-10:
+    #   https://github.com/chocolate-doom/chocolate-doom/pull/1257
+    (fetchpatch {
+      name = "fno-common.patch";
+      url = "https://github.com/chocolate-doom/chocolate-doom/commit/a8fd4b1f563d24d4296c3e8225c8404e2724d4c2.patch";
+      sha256 = "1dmbygn952sy5n8qqp0asg11pmygwgygl17lrj7i0fxa0nrhixhj";
+    })
+  ];
+
   postPatch = ''
     sed -e 's#/games#/bin#g' -i src{,/setup}/Makefile.am
   '';