secure_storage: warn when there is no ITS store module implementation

Output a CMake error when the ITS store module is enabled but no
implementation ended up enabled (due to unfulfilled prerequisites).
This is to make it more clear than undefined references at link time.
Not a fatal error because CMake cannot fail for the twister filtering
to work on the tests.

Signed-off-by: Tomi Fontanilles <[email protected]>

Author: tomi-font

subsys/secure_storage/src/its/CMakeLists.txt

@@ -30,3 +30,9 @@ zephyr_library_sources_ifdef(CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_ZMS
 zephyr_library_sources_ifdef(CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_SETTINGS
   store/settings.c
 )
+if (CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_NONE)
+  message(ERROR "
+    The secure storage ITS module is enabled but has no implementation.
+    (CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_NONE)
+    ")
+endif()