IVGCVSW-3656 Make the reference backend optional

 * Made the build of the reference backend depend on a new ARMCOMPUTEREF
   macro
 * Made the relevant targets dependent on the ref backend
 * Moved Cl and Neon static registry initializers to separate files
 * Wrapped some of the unit tests into proper ifdefs where necessary

Change-Id: I7f2c42699682630233a4c4b6aed2f005083de189
Signed-off-by: Matteo Martincigh <matteo.martincigh@arm.com>
diff --git a/src/backends/backendsCommon/test/DynamicBackendTests.cpp b/src/backends/backendsCommon/test/DynamicBackendTests.cpp
index e42a08a..17a99f8 100644
--- a/src/backends/backendsCommon/test/DynamicBackendTests.cpp
+++ b/src/backends/backendsCommon/test/DynamicBackendTests.cpp
@@ -61,6 +61,12 @@
 ARMNN_SIMPLE_TEST_CASE(RuntimeInvalidDynamicBackends, RuntimeInvalidDynamicBackendsTestImpl);
 ARMNN_SIMPLE_TEST_CASE(RuntimeInvalidOverridePath, RuntimeInvalidOverridePathTestImpl);
 
+#if defined(ARMCOMPUTEREF_ENABLED)
+
+// This test unit needs the reference backend, it's not available if the reference backend is not built
+
 ARMNN_SIMPLE_TEST_CASE(CreateReferenceDynamicBackend, CreateReferenceDynamicBackendTestImpl);
 
+#endif
+
 BOOST_AUTO_TEST_SUITE_END()