Use ctest for running the freertos application

Change-Id: Iff207d9bd8f8406c645b087560212fb0aabe82f4
diff --git a/applications/freertos/CMakeLists.txt b/applications/freertos/CMakeLists.txt
index f803d43..0bd1de6 100644
--- a/applications/freertos/CMakeLists.txt
+++ b/applications/freertos/CMakeLists.txt
@@ -22,6 +22,6 @@
     return()
 endif()
 
-ethosu_add_executable(freertos PRIVATE
+ethosu_add_executable_test(freertos PRIVATE
     SOURCES main.cpp
     LIBRARIES freertos_kernel)