error: …/build/Release/Defaults_Defaults.bundle: No such file or directory

[F1248]

This is probably a beginner's mistake, but I can't find anything about this error anywhere, and it's completely reproducible, even on GitHub Runners and with a fresh Xcode project. Any help would be greatly appreciated.

• macOS Sequoia 15.2 (24C101)
• Xcode Version 16.2 (16C5032a)
• Defaults Version 9.0.0

When following Defaultss installation instructions, building and archiving from Xcode still works fine, but building with xcodebuild always fails with this error:

Copy /Users/user/DefaultsTest/build/Release/DefaultsTest.app/Contents/Resources/Defaults_Defaults.bundle /Users/user/DefaultsTest/build/Release/Defaults_Defaults.bundle (in target 'DefaultsTest' from project 'DefaultsTest')
    cd /Users/user/DefaultsTest
    builtin-copy -exclude .DS_Store -exclude CVS -exclude .svn -exclude .git -exclude .hg -resolve-src-symlinks /Users/user/DefaultsTest/build/Release/Defaults_Defaults.bundle /Users/user/DefaultsTest/build/Release/DefaultsTest.app/Contents/Resources
error: /Users/user/DefaultsTest/build/Release/Defaults_Defaults.bundle: No such file or directory (in target 'DefaultsTest' from project 'DefaultsTest')

I made a fresh, reproducible Xcode project here:
https://github.com/F1248/DefaultsTest

And a failing GitHub Action here:
https://github.com/F1248/DefaultsTest/actions/runs/12303972248/job/34340347771