Exclude not working with absolute path in some cases

These are all executed from the `selene-test` workspace.

Works:
```
exclude = ["**/file.lua"]
```
```
selene C:\Users\chris\OneDrive\Documents\selene-test\src\file.lua
```

Works:
```
exclude = ["src/**"]
```
```
selene src/file.lua
```

Doesn't work:
```
exclude = ["src/**"]
```
```
selene C:\Users\chris\OneDrive\Documents\selene-test\src\file.lua
```