Can't add as Swift Package in Xcode

[crazytonyli]

Steps to reproduce:

1. Create an empty Xcode project.
2. Go to "Package Dependencies" in the project settings.
3. Add this package as Swift Package.

Xcode fails to add the library due to failing to resolve package manifest.

The issue is caused by the way SwiftLint is integrated. It appears, while resolving package manifest, Xcode/SPM uses a virtual file system where only Package.swift is available and the .swiftlint.yml file doesn't exist in the file system.