Int function should return a value

With gcc-14 toolchain the dynamic and dynamic-double testcases were
ending up with SIGILL (Illegal instruction) without this update.

tests/Sanity/smoke-test/dynamic-double/mutatee.cpp

@@ -19,6 +19,7 @@ void incr2(void)
 int function_name(void)
 {
 	fprintf(stderr, "FUNCTION EXECUTED. VALUE = %i\n", a);
+        return 0;
 }
 
 int main(int argc, char **argv)

tests/Sanity/smoke-test/dynamic/mutatee.cpp

@@ -14,6 +14,7 @@ void incr(void)
 int function_name(void)
 {
 	fprintf(stderr, "FUNCTION EXECUTED. VALUE = %i\n", a);
+        return 0;
 }
 
 int main(int argc, char **argv)