Issue:
Xcode is unable to fetch your private Swift Package Manager dependencies and because of that, the Xcode Test or the Xcode Archive Step fails.
Possible solutions:
By default, Xcode isn't using the system source control manager settings. To make it do so:
Open the relevant Step in the Workflow Editor.
Find and open the Debug input group.
In the Additional options for xcodebuild call input, pass the following flag:
-scmProvider system