surreal-engine: fix build with sdl2-compat

+2
+2
pkgs/by-name/su/surreal-engine/package.nix
··· 9 9 openal, 10 10 pkg-config, 11 11 SDL2, 12 + libX11, 12 13 stdenv, 13 14 vulkan-loader, 14 15 wayland, ··· 39 40 libffi 40 41 openal 41 42 SDL2 43 + libX11 42 44 vulkan-loader 43 45 wayland 44 46 waylandpp