util: silence out-of-bounds read warning

gcc -fanalyze complains because it doesn't know the __stop section is
always greater than the __start section so it complains that we're
eventually reading past our __start section. Let's silence that with a
simple check.

src/util-munit.h

@@ -52,7 +52,7 @@
  */
 #define foreach_test(t_) \
 	for (const struct test_function *t_ = &__start_test_functions_section; \
-	     t_ < &__stop_test_functions_section; \
+	     t_ < &__stop_test_functions_section && t < &__start_test_functions_section; \
 	     t_++)
 
 typedef MunitResult (*munit_test_func_t)(const MunitParameter params[], void *user_data);