make check fails with errors for cro3_paths

`make check` fails with the errors below.

```
cargo check
Checking cro3 v0.1.2 (/work/cro3)
error[E0432]: unresolved import `cro3::util::cro3_paths`
--> src/cmd/servo.rs:33:17
|
33 | use cro3::util::cro3_paths::cro3_dir;
| ^^^^^^^^^^ could not find `cro3_paths` in `util`

error[E0432]: unresolved import `cro3::util::cro3_paths`
--> src/cmd/servo.rs:34:17
|
34 | use cro3::util::cro3_paths::gen_path_in_cro3_dir;
| ^^^^^^^^^^ could not find `cro3_paths` in `util`

error[E0432]: unresolved import `cro3::util::cro3_paths`
--> src/cmd/setup.rs:14:17
|
14 | use cro3::util::cro3_paths::gen_path_in_cro3_dir;
| ^^^^^^^^^^ could not find `cro3_paths` in `util`

For more information about this error, try `rustc --explain E0432`.

```

But there is `src/util/cro3_paths.rs`.