It is kind of late in build cycle but I think we gotta correct this. New "Save Build Console" feature added in bug 294106 is a wanted feature but it is implemented in an awkward way from user point of view. The current workflow requires user to setup logging in properties before build occurs. It is prone to accidental overwriting as new build will overwrite the old log silently.
My suggestion is attached to bug 306222. It changes "Save Build Console" to straightforward flow: 1. User runs builds
2. User spots interesting output and clicks "Save Output" button saving the build log in chosen file via file selection dialog.
Additional bonus that it will work with non-C projects (builders that not aware of CDT configurations).
I think we better include the change to 7.0 now before the users develop a habit.