layers: Change to including vk_safe_struct code.
Cmake on windows cannot handle multiple projects using generated library code.
diff --git a/layers/unique_objects.cpp b/layers/unique_objects.cpp
index 1a79d77..0d81c80 100644
--- a/layers/unique_objects.cpp
+++ b/layers/unique_objects.cpp
@@ -41,6 +41,9 @@
#include "vk_layer_data.h"
#include "vk_layer_utils.h"
+// This intentionally includes a cpp file
+#include "vk_safe_struct.cpp"
+
#include "unique_objects_wrappers.h"
namespace unique_objects {