Don't build with X11 by default since it's not included with the latest versions of Mac OS X. Cocoa is the preferred path here.
--- a/include/SDL_config_macosx.h Tue Dec 11 12:01:30 2012 -0800
+++ b/include/SDL_config_macosx.h Tue Dec 11 12:03:00 2012 -0800
@@ -130,7 +130,7 @@
/* Enable various video drivers */
#define SDL_VIDEO_DRIVER_COCOA 1
#define SDL_VIDEO_DRIVER_DUMMY 1
-#define SDL_VIDEO_DRIVER_X11 1
+#define SDL_VIDEO_DRIVER_X11 0
#define SDL_VIDEO_DRIVER_X11_DYNAMIC "/usr/X11R6/lib/libX11.6.dylib"
#define SDL_VIDEO_DRIVER_X11_DYNAMIC_XEXT "/usr/X11R6/lib/libXext.6.dylib"
#define SDL_VIDEO_DRIVER_X11_DYNAMIC_XINERAMA "/usr/X11R6/lib/libXinerama.1.dylib"