Make npm mv rather than rename to fix the build
Make npm mv rather than rename to fix the build

Summary:
This is ugly, but the accepted solution (apparently https://github.com/npm/npm/issues/9863)
and it is localized enough that I don't feel too bad.

Test Plan: Passes on Changes. Commented out, it fails.

Reviewers: anupc, paulruan

Reviewed By: paulruan

Differential Revision: https://tails.corp.dropbox.com/D196973

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