[REG 4.8->4.9]: When starting Qt Creator where it has Qt 5.8 Boot2Qt based kits then it will end up losing some of the settings for this and make them invalid

When starting Qt Creator where it has Qt 5.8 Boot2Qt based kits then it will end up losing some of the settings for this and make them invalid. This works fine in Qt Creator 4.8 but in Qt Creator 4.9 it makes them invalid indicating that the compiler is not compatible or worse still fails to display the kit altogether.

This was reproducible by having the 5.8 Boundary Devices installation already installed and by installing it after the Qt Creator 4.9.1 was installed.