final line printed should have the file name

Example:
```
$ ARCH=riscv /android2/reduce/reduce.py prep net/netlink/af_netlink.i
...
Example Usage: $ cvise test.sh string.i
```
It would be cool if we printed
```
Example Usage: $ cvise test.sh af_netlink.i
```
instead. We should know what the reduced file's name is.