IVGCVSW-1987 : registry for backend creation functions (factories)

Change-Id: I13d2d3dc763e1d05dffddb34472bd4f9e632c776
diff --git a/src/backends/CMakeLists.txt b/src/backends/CMakeLists.txt
index ea5ad78..0bc6888 100644
--- a/src/backends/CMakeLists.txt
+++ b/src/backends/CMakeLists.txt
@@ -4,6 +4,8 @@
 #
 
 list(APPEND armnnBackendsCommon_sources
+    BackendRegistry.cpp
+    BackendRegistry.hpp
     CpuTensorHandle.cpp
     CpuTensorHandleFwd.hpp
     CpuTensorHandle.hpp