Fix snapshot build
Fix snapshot build

Summary:
Removal of some dependencies from base snapshots has subtly broken the Changes Changes build.
Snapshot builds succeed, but fail once activated.
This provides the missing package that seems to resolve the issue.
I ran two no-snapshot builds:
 Without this change: https://changes.build.itc.dropbox.com/single_build/ab7c567e894548efaf96411e1e3e85bc/
 With this change: https://changes.build.itc.dropbox.com/single_build/826a0e40ed5d425c83f06ccd6fa69e92/

Hat tip to @paulruan for the no_snapshot parameter, which made testing this not terrible.

Test Plan: Changes

Reviewers: nate

Reviewed By: nate

Subscribers: changesbot, paulruan

Differential Revision: https://tails.corp.dropbox.com/D165818

dropbox/changes,dropbox/changes,dropbox/changes,dropbox/changes