Seems like the profile manager puts user profiles under mozilla\dist. So when you do a clobber build, user profiles get deleted. It would be better if user profiles were tolerant of a clobber build. For me, this issue is a real time waster, considering how much hand-tweaking there is in setting up a profile right now.
Same issue as 6464, except it's in the build environment. Your workaround is to explicitly name the directory where you want it to go. *** This bug has been marked as a duplicate of 6464 ***
Moving all Profile Manager bugs to new Profile Manager Backend component. Profile Manager component to be deleted.