construo: fix build after libGL transition

pkgs/games/construo/default.nix

···
-{ stdenv, fetchurl, libX11, zlib, xproto, libGLU_combined ? null, freeglut ? null }:
+{ stdenv, fetchurl, libX11, zlib, xproto, libGL ? null, freeglut ? null }:
 
 stdenv.mkDerivation rec {
   name = "construo-${version}";
···
   };
 
   buildInputs = [ libX11 zlib xproto ]
-    ++ stdenv.lib.optional (libGLU_combined != null) mesa
+    ++ stdenv.lib.optional (libGL != null) libGL
     ++ stdenv.lib.optional (freeglut != null) freeglut;
 
   preConfigure = ''

pkgs/top-level/all-packages.nix

···
   confd = callPackage ../tools/system/confd { };
 
   construoBase = lowPrio (callPackage ../games/construo {
-    mesa = null;
+    libGL = null;
     freeglut = null;
   });
 
   construo = construoBase.override {
-    inherit mesa freeglut;
+    inherit  freeglut;
+    libGL = libGLU_combined;
   };
 
   crack_attack = callPackage ../games/crack-attack { };