Ignores() seems to behave differently on windows

[alasdairhurst]

I notice you have a lot of similar issues related to windows paths. This one is specifically relative paths:

On unix, this throws an error.
cwd is /mnt/c/module

ignore.ignores('/mnt/c/module/package.json')

fatal error RangeError: path should be a `path.relative()`d string, but got "/mnt/c/module/package.json"

On windows it behaves differently. Possibly a false positive, but there's no error:

cwd is C:\module

ignore.ignores('C:\module\package.json')

[kaelzhang]

landed in 5.1.1

https://github.com/kaelzhang/node-ignore/releases/tag/5.1.1