error message if user specifies SDL cmd line option when SDL is disabled

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/vl.c b/vl.c
index 1cb7ce2..4ca4192 100644
--- a/vl.c
+++ b/vl.c
@@ -2625,6 +2625,14 @@
             case QEMU_OPTION_sdl:
                 display_type = DT_SDL;
                 break;
+#else
+            case QEMU_OPTION_no_frame:
+            case QEMU_OPTION_alt_grab:
+            case QEMU_OPTION_ctrl_grab:
+            case QEMU_OPTION_no_quit:
+            case QEMU_OPTION_sdl:
+                fprintf(stderr, "SDL support is disabled\n");
+                exit(1);
 #endif
             case QEMU_OPTION_pidfile:
                 pid_file = optarg;