Generated mocks don't work on Xcode Cloud

[legoesbenr]

New Issue Checklist

• [ X] I updated the framework and generator to the latest version
• [ X] I searched the existing GitHub issues and list of common problems

Overview

I have recently run into a weird issue with mocking in our iOS unit tests.
Mocking and our unit tests works just fine locally and it has also worked fine when building on Xcode Cloud.
Until recently, when it started to throw this error:

Operation '<MockingbirdGenerator.GenerateFileOperation: 0x7fb81740beb0>' failed with error 'Error Domain=NSCocoaErrorDomain Code=516 "“AppNameMocks.generated.swift” couldn’t be moved to “MockingbirdMocks” because an item with the same name already exists."

From the error message the problem is quite obvious, but there are not changes to our the post build script, which have worked fine for almost a year on Xcode Cloud.
Our PostBuildScript looks like this:

set -eu

# Prevent Xcode 13 from running this script while indexing.
[[ "${ACTION}" == "indexbuild" ]] && exit 0

# Infer the derived data location from the build environment.
[[ -z "${DERIVED_DATA+x}" ]] && DERIVED_DATA="$(echo "${BUILD_ROOT}" | sed -n 's|\(.*\)/Build/.*|\1|p')"

"${DERIVED_DATA}/SourcePackages/checkouts/mockingbird/mockingbird" generate --targets "AppName" "AppName" --outputs "${SRCROOT}/MockingbirdMocks/AppNameMocks.generated.swift" "${SRCROOT}/MockingbirdMocks/AppNameMocks.generated.swift"

Environment

• Mockingbird via SPM version 0.20.0
• Xcode 15.4 and Swift version 5.2
• Swift Package manager
• XCTest
• Custom configuration
  • none

[legoesbenr]

I found that we have two targets after each other in the command and the output defined twice, in the command.
Reducing this to one target and one output parameter fixed it. Don't know how this worked for 1+ year.

Also; the documentation is extremely thin and actually wrong compared to the example (if you look at the post build script).