Force garbage collection more aggressively during package DB sync.
Force garbage collection more aggressively during package DB sync.

This is an effort to keep the `meteor --get-ready` command from running
out of memory during Circle CI tests, as mentioned in this comment:
https://github.com/meteor/meteor/pull/8327#issuecomment-284431618

Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor