pkgbuild on Tahoe fails to build packages if any directory name contains non-ascii characters

pkgbuild on Tahoe (26.3.1) fails to build packages if any directory name contains non-ascii characters.

pkgbuild is able to build successfully with the same source data on previous versions on macOS, so this is a regression and prevents us from build able to build our products on macOS 26.

Example that demonstrates the issue:

mkdir -p MyAppData/Taishōgoto
echo "Testing" >> MyAppData/Taishōgoto/Content.txt
pkgbuild --identifier com.example.MyAppData --install-location '/Library/Application Support/MyAppData' --root MyAppData myappdata.pkg

Error messages:

parent directory ./Taishōgoto does not exist
pkgbuild: error: Cannot write package to "myappdata.pkg". (The file “package.bom” couldn’t be saved in the folder “NSIRD_pkgbuild_52fPuN”.)

I have submitted this via Feedback Assistant (FB22312299).

I have not found a workaround. Tried copying pkgbuild from Sequoia but the problem persisted, probably because the buggy code is in PackageKit rather than the tool itself.

pkgbuild on Tahoe fails to build packages if any directory name contains non-ascii characters
 
 
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