My ui.c contains lv_obj_t * target = lv_event_get_target(e); in 147 places which is not used for anything. This generates warning: unused variable 'target' [-Wunused-variable] 147 times since it is not used.
Why is this line of code being generated if it is not used?
Your toolchain seems to be picky about unused variables, in most tools this only throws a warning by default and compiles the project fine.
You can modify this behaviour by using -Wno-unused-variable argument with your compiler.