make CPU backend auto-register (#1478)

src/ngraph/runtime/cpu/cpu_backend.cpp

@@ -17,6 +17,7 @@
 #include <tbb/tbb_stddef.h>
 
 #include "ngraph/graph_util.hpp"
+#include "ngraph/runtime/backend_manager.hpp"
 #include "ngraph/runtime/cpu/cpu_backend.hpp"
 #include "ngraph/runtime/cpu/cpu_call_frame.hpp"
 #include "ngraph/runtime/cpu/cpu_external_function.hpp"
@@ -43,6 +44,16 @@ extern "C" void delete_backend(runtime::Backend* backend)
     delete backend;
 }
 
+namespace
+{
+    static class CPUStaticInit
+    {
+    public:
+        CPUStaticInit() { runtime::BackendManager::register_backend("CPU", new_backend); }
+        ~CPUStaticInit() {}
+    } s_cpu_static_init;
+}
+
 shared_ptr<runtime::cpu::CPU_CallFrame> runtime::cpu::CPU_Backend::make_call_frame(
     const shared_ptr<runtime::cpu::CPU_ExternalFunction>& external_function)
 {