CMake: fix encrypted project flash arg file generation See merge request espressif/esp-idf!5741
@@ -1,3 +1,3 @@
--encrypt ${ESPTOOLPY_FLASH_PROJECT_OPTIONS}
-$<JOIN:$<TARGET_PROPERTY:flash_project_args_target,FLASH_PROJECT_ARGS>,
+$<JOIN:${FLASH_PROJECT_ARGS},
>