surreal-engine: fix build with sdl2-compat

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