IVGCVSW-3418 Add Arm NN front end support for the new Stack layer

 * Added new StackLayer class
 * Made necessary changes to Descriptors, ILayerSupport, ILayerVisitor, etc.
 * Added unit tests

Signed-off-by: Matthew Jackson <matthew.jackson@arm.com>
Change-Id: Ieb97a928a342ffe1901c6058eb895711c358fd3d
diff --git a/src/armnnSerializer/Serializer.cpp b/src/armnnSerializer/Serializer.cpp
index c9719aa..0a9e335 100644
--- a/src/armnnSerializer/Serializer.cpp
+++ b/src/armnnSerializer/Serializer.cpp
@@ -925,6 +925,13 @@
     CreateAnyLayer(flatBufferLayer.o, serializer::Layer::Layer_NormalizationLayer);
 }
 
+void SerializerVisitor::VisitStackLayer(const armnn::IConnectableLayer* layer,
+                                        const armnn::StackDescriptor& stackDescriptor,
+                                        const char* name)
+{
+    throw UnimplementedException("SerializerVisitor::VisitStackLayer not yet implemented");
+}
+
 void SerializerVisitor::VisitStridedSliceLayer(const armnn::IConnectableLayer* layer,
                                                const armnn::StridedSliceDescriptor& stridedSliceDescriptor,
                                                const char* name)