cmake: allow to disable automatic cmake run

The new cmake integration (running cmake in background, cache inspection, etc) is really nice. However, please consider an option to disable automatic cmake running in background.
Sometimes, it is useful to clear and rebuild a whole workspace at the commandline. Currently, this heavily interferes with qtcreator, requiring to stop and restart qtcreator afterwards.
It would be great to have a toggle somewhere to temporarily disable cmake background jobs.