rotation: fix switch statement for rotation

Change-Id: I29e594791b3a149f08df95fe37309a1ed82784ad
diff --git a/minuitwrp/libminuitwrp_defaults.go b/minuitwrp/libminuitwrp_defaults.go
index 802533a..2f82c6e 100644
--- a/minuitwrp/libminuitwrp_defaults.go
+++ b/minuitwrp/libminuitwrp_defaults.go
@@ -132,8 +132,11 @@
 	var tw_rotation = getMakeVars(ctx, "TW_ROTATION")
 	switch tw_rotation {
 	case "0":
+		fallthrough
 	case "90":
+		fallthrough
 	case "180":
+		fallthrough
 	case "270":
 		cflags = append(cflags, "-DTW_ROTATION="+tw_rotation)
 	default: