Add test message handler to be used for testing

It is like message handler but it does not process any
inferences. They are simply queue and never executed.

Change-Id: I131c3c779b616e82d650ff03e3723dc607de58bf
diff --git a/applications/message_handler/CMakeLists.txt b/applications/message_handler/CMakeLists.txt
index 6928c2d..5e95bdd 100644
--- a/applications/message_handler/CMakeLists.txt
+++ b/applications/message_handler/CMakeLists.txt
@@ -16,13 +16,13 @@
 # limitations under the License.
 #
 
-if (NOT TARGET freertos_kernel)
-    message("Not building ethosu_message_dispatcher, required freertos not built.")
+if(NOT TARGET freertos_kernel)
+    message("Skipping message handler")
     return()
 endif()
 
 # Split total tensor arena equally for each NPU
-if (TARGET ethosu_core_driver AND ETHOSU_TARGET_NPU_COUNT GREATER 0)
+if(TARGET ethosu_core_driver AND ETHOSU_TARGET_NPU_COUNT GREATER 0)
     set(NUM_ARENAS ${ETHOSU_TARGET_NPU_COUNT})
 else()
     set(NUM_ARENAS 1)
@@ -41,10 +41,10 @@
 
 ethosu_add_executable(message_handler
     SOURCES
-        main.cpp
+    main.cpp
     LIBRARIES
-        message_handler_lib
-        freertos_kernel)
+    message_handler_lib
+    freertos_kernel)
 
 target_include_directories(message_handler PRIVATE
     indexed_networks