Changes simulation ending mechanism (exit function)

As higher optimization might actually schedule a jump to self while waiting for timer interrupts this is a more robust implementation in that sense

test/threadx/run_threadx_test.sh

@@ -21,7 +21,6 @@ trap 'rm -f "$log_file"' EXIT
 "$simulator" \
     --isa="$isa" \
     -f "$elf" \
-    -p tb.top.core.finish_condition=1 \
     -m 10s \
     | tee "$log_file"