polymc: use LD_LIBRARY_PATH, not GAME_LIBRARY_PATH

Since 1.4.0, PolyMC simply uses LD_LIBRARY_PATH, rather than a custom
GAME_LIBRARY_PATH variable.

This change was made in PolyMC/PolyMC#893, which also fixes the in-tree
Nix wrapper script to match. NixOS/nixpkgs#182621 updated our PolyMC to
1.4.0, but did not port the wrapper changes along.

The lack of LD_LIBRARY_PATH causes libpulse to be unavailable,
causing the sound issues observed in NixOS/nixpkgs#184189.

Change-Id: I4042f774c1fc804609dbaa3f4206ca0dd8ab20b3

pkgs/games/polymc/default.nix

@@ -54,7 +54,7 @@ stdenv.mkDerivation rec {
   in ''
     # xorg.xrandr needed for LWJGL [2.9.2, 3) https://github.com/LWJGL/lwjgl/issues/128
     wrapQtApp $out/bin/polymc \
-      --set GAME_LIBRARY_PATH /run/opengl-driver/lib:${libpath} \
+      --set LD_LIBRARY_PATH /run/opengl-driver/lib:${libpath} \
       --prefix POLYMC_JAVA_PATHS : ${lib.makeSearchPath "bin/java" jdks} \
       --prefix PATH : ${lib.makeBinPath [ xorg.xrandr ]}
   '';