fix crash in build.rs when installing from source on linux

[savente93]

The current build.rs fails to compile "widows resources" when installing from source on Linux, so I added a !cfg(windows) to fix that. That's all.

Sanity check:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Code changes

(Delete or ignore this section for documentation changes)

• Are you doing the PR on the next branch?

If the change is a new feature or adding to/changing an existing one:

• Have you created/updated the relevant documentation page(s)?

[Keats]

I believe you can wrap L32 in the if cfg(windows) instead?

[Keats]

Thanks!