When the cmake configuration changes, BuildDirManager checks whether
the new configuration differs from the current configuration.
In case of differences a dialog is opened and the user must decide if
the changes shall be applied or rejected.
When the user changes the cmake configuration in the projects page the
dialog will open as well. This is unencessary since the user already
decided to apply the changes.

Let BuildDirManager not check for changes if the configuration was
changed by the user via the projects page.

Change-Id: I736ee7f4dee99fe707f2931c73b287231b1daa1d
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>