layers: GH1115 Add missing VK_LAYER_EXPORT decorations

Functions in the vk_layer_extension_utils file were
not getting exported correctly.

Change-Id: If1bf6456cb8e79a1b6292ea76bd72e3e89a2b430
diff --git a/layers/vk_layer_extension_utils.h b/layers/vk_layer_extension_utils.h
index 0f249b7..b593768 100644
--- a/layers/vk_layer_extension_utils.h
+++ b/layers/vk_layer_extension_utils.h
@@ -30,11 +30,11 @@
  */
 extern "C" {
 
-VkResult util_GetExtensionProperties(const uint32_t count, const VkExtensionProperties *layer_extensions, uint32_t *pCount,
-                                     VkExtensionProperties *pProperties);
+VK_LAYER_EXPORT VkResult util_GetExtensionProperties(const uint32_t count, const VkExtensionProperties *layer_extensions,
+                                                     uint32_t *pCount, VkExtensionProperties *pProperties);
 
-VkResult util_GetLayerProperties(const uint32_t count, const VkLayerProperties *layer_properties, uint32_t *pCount,
-                                 VkLayerProperties *pProperties);
+VK_LAYER_EXPORT VkResult util_GetLayerProperties(const uint32_t count, const VkLayerProperties *layer_properties, uint32_t *pCount,
+                                                 VkLayerProperties *pProperties);
 
 } // extern "C"
 #endif // LAYER_EXTENSION_UTILS_H