headers: Add vk_sdk_platform.h for Win/Linux differences
diff --git a/demos/cube.c b/demos/cube.c
index 183d35d..f388b4e 100644
--- a/demos/cube.c
+++ b/demos/cube.c
@@ -43,6 +43,7 @@
 
 #include "icd-spv.h"
 
+#include "vk_sdk_platform.h"
 #include "linmath.h"
 #include <png.h>