[REG Qt 5.5.0 -> Qt 5.5.1] Pointless subdir "." in Qt Quick UI project

1. Run Creator on current Qt 5.5 branch.
2. Create a new Qt Quick UI project.
   In Projects view, you'll see a pointless subdirectory ".":
   

The file should be listed right at the root node. This works correctly when Creator is running on Qt 5.5.0.

This bug looks just like QTCREATORBUG-14994 and I assume it has same reason, a behavior change in QDir::relativeFilePath().