[AVR] qbs.targetOS cleanups each time from Kit when QtC re-started

I have created the baremetal AVR GCC Kit, and I see that each time when I run the QtC, then the qbs.targetOS resets to undefined.

Also I did not see qbs.architecture property at all (it should be as 'avr').

I see this via Build&Run->Qbs->AVR kit

• If then I run the 'Apply' button, then qbs.targetOS resets to empty [].
• If then I close the 'Options" page ans open it again, than I see that qbs.targetOS also resets to empty [].

Also, somethime qbs.architecture appeared as 'avr', and somethime this properti not present at all from the "Build&Run->Qbs->AVR kit". So, the behavior is strange.