rustc --print-file-name doesn't print ".exe" on Windows

```
rustc --print-file-name hello.rs
```

prints "hello" instead of "hello.exe".

```
rustc -o hello2.exe --print-file-name hello.rs
```

prints "hello2" instead of "hello2.exe".

If no "--print-file-name", it do create hello.exe / hello2.exe file.
