Missing package product

作者执行下列步骤解决了

1. Kill xcode
2. Then completely remove the derived data directory (empty trash just to be absolutely sure).
3. Restart Xcode
4. Reset Swift package cache

第四步骤

传送门
https://forums.swift.org/t/missing-package-product-error-for-all-local-swift-packages-when-switching-git-branches/38041