IVGCVSW-3739 Add serialization support for Abs

Signed-off-by: FinnWilliamsArm <Finn.Williams@arm.com>
Change-Id: I42c348515f3f93efc2e0570bbebdc77306f12468
diff --git a/src/armnnSerializer/Serializer.cpp b/src/armnnSerializer/Serializer.cpp
index a8d9c23..595573c 100644
--- a/src/armnnSerializer/Serializer.cpp
+++ b/src/armnnSerializer/Serializer.cpp
@@ -107,7 +107,10 @@
 
 void SerializerVisitor::VisitAbsLayer(const armnn::IConnectableLayer* layer, const char* name)
 {
-    throw UnimplementedException("SerializerVisitor::VisitAbsLayer is not implemented");
+    auto flatBufferBaseLayer = CreateLayerBase(layer, serializer::LayerType::LayerType_Abs);
+    auto flatBufferAbsLayer  = serializer::CreateAbsLayer(m_flatBufferBuilder, flatBufferBaseLayer);
+
+    CreateAnyLayer(flatBufferAbsLayer.o, serializer::Layer::Layer_AbsLayer);
 }
 
 // Build FlatBuffer for Activation Layer