QBS project manager and Android "automatic kit" generation cause needless memory churn

On startup, the android integration creates kits for all matching Qt versions, and sets the sticky bit on all their KitInformation. This includes the QbsKitInformation. The QbsKitInformation is peculiar in that it leaves its ID string empty. Therefore, when loading the sticky bits, it is omitted (see Kit::Kit(const QVariantMap &data)). Thus, all android-related kits with QbsKitInformation are "changed" every time we start. This causes a kitUpdated() signal to be emittted, which in turn causes the QbsProjectManager to rebuild its internal kit representation from scratch.

Measurements indicate that this amounts to about 10% of all memory allocations and more than 15% of all memory releases during startup.