$NetBSD$

Use X11_LDFLAGS to fix linking.

--- src/Makefile.orig	2017-07-15 21:27:56.000000000 +0000
+++ src/Makefile
@@ -63,7 +63,7 @@ ifeq ($(WITH_SDL2), 1)
 		ifeq ($(PLATFORM), WINDOWS)
 			LIBS+= -lopengl32
 		else
-			LIBS+= -lGL
+			LIBS+= -lGL $(X11_LDFLAGS)
 		endif
 		IDOBJECTS+= id_vl_sdl2gl.o 
 	endif
