Looks like about six hours ago, a commit was pushed to https://github.com/thebrowsercompany/swift-windowsfoundation that means it can no longer be pulled in by xcodebuild. (Not sure why it's succeeding on Linux; you'd think xcodebuild and SPM would resolve dependencies the same way.) Sometime thereafter, the repository was archived, so we shouldn't expect an update to come and fix it. I can't point it at an older commit because one of our dependencies also points at main, so SPM will complain about the mismatched commits.