Bugfix for tarmac traces being always enabled

Change-Id: Ide11895f0ce96d48d14210253c25d2ac624cf856
diff --git a/targets/corstone-300/CMakeLists.txt b/targets/corstone-300/CMakeLists.txt
index a409a97..b129b71 100644
--- a/targets/corstone-300/CMakeLists.txt
+++ b/targets/corstone-300/CMakeLists.txt
@@ -60,11 +60,18 @@
 set(Python3_FIND_STRATEGY LOCATION)
 find_package(Python3 COMPONENTS Interpreter)
 ethosu_get_architecture(${ETHOSU_TARGET_NPU_CONFIG})
-set(ETHOSU_COMMAND_DEFAULT ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../../scripts/run_ctest.py
+set(ETHOSU_COMMAND_OPTIONS
         -t corstone-300
         -a ethos-${ETHOSU_ARCH}
         -m ${ETHOSU_NUM_MACS}
-        $<$<BOOL:ETHOSU_CTEST_TARMAC_TRACE>:--tarmac>
+        CACHE INTERNAL "Default test command options")
+
+if (ETHOSU_CTEST_TARMAC_TRACE)
+    list(APPEND ETHOSU_COMMAND_OPTIONS "--tarmac")
+endif()
+
+set(ETHOSU_COMMAND_DEFAULT ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../../scripts/run_ctest.py
+        ${ETHOSU_COMMAND_OPTIONS}
     CACHE INTERNAL "Default test command")
 
 # Enable trustzone support in core_software