Fix missing namespace in sys crate build script

[DanielSporysz]

The build script of sys crate is throwing an error due to undeclared types. Let's fix it by adding namespaces.

[HoKim98]

File is imported on line 177.

dlib-face-recognition/sys/build.rs

Line 177 in 079158d

use std::fs::File;

Path is imported on line 4.

dlib-face-recognition/sys/build.rs

Line 4 in 079158d

use std::path::Path;

So I think there is no problem building on windows. Could you check and comment on?

[DanielSporysz]

@HoKim98 the build was failing, until I went to .cargo\registry\src to edit the source code with these changes. I can see the imports and it's weird I saw namespace errors, but this is what fixed my failures. 🤔

[HoKim98]

That's strange. Let me check on a windows VM and comment again.

[orpos]

for me it was giving the same error but when i used this pr on the cargo file it worked