IVGCVSW-4246 Clean build of backends with -Wextra

Change-Id: I9e8d5576b3ec04c871785d5f2f9545bf1136e59b
Signed-off-by: Derek Lamberti <derek.lamberti@arm.com>
diff --git a/include/armnn/backends/IBackendInternal.hpp b/include/armnn/backends/IBackendInternal.hpp
index 3296d81..3533ace 100644
--- a/include/armnn/backends/IBackendInternal.hpp
+++ b/include/armnn/backends/IBackendInternal.hpp
@@ -127,7 +127,7 @@
     /// (Optional) Register TensorHandleFactories
     /// Either this method or CreateMemoryManager() and
     /// IWorkloadFactory::CreateTensor()/IWorkloadFactory::CreateSubtensor() methods must be implemented.
-    virtual void RegisterTensorHandleFactories(class TensorHandleFactoryRegistry& registry) {}
+    virtual void RegisterTensorHandleFactories(class TensorHandleFactoryRegistry& /*registry*/) {}
 
     /// Returns the version of the Backend API
     static constexpr BackendVersion GetApiVersion() { return BackendVersion(1, 0); }
diff --git a/include/armnn/backends/ITensorHandle.hpp b/include/armnn/backends/ITensorHandle.hpp
index e1b80b8..6ef0e32 100644
--- a/include/armnn/backends/ITensorHandle.hpp
+++ b/include/armnn/backends/ITensorHandle.hpp
@@ -6,6 +6,8 @@
 
 #include <armnn/MemorySources.hpp>
 
+#include <boost/core/ignore_unused.hpp>
+
 namespace armnn
 {
 
@@ -71,7 +73,11 @@
     /// \param memory base address of the memory being imported.
     /// \param source source of the allocation for the memory being imported.
     /// \return true on success or false on failure
-    virtual bool Import(void* memory, MemorySource source) { return false; };
+    virtual bool Import(void* memory, MemorySource source)
+    {
+        boost::ignore_unused(memory, source);
+        return false;
+    };
 };
 
 }