[Selective build] Enable selective build in VariablType
Summary:
Quick fix due to code merging. With this feature working, the total size reduction in Android is 664 KB (Pytorch -26 KB and papaya - 639 KB)
https://fburl.com/unigraph/c726gvb1
Test Plan: CI
Reviewed By: kwanmacher
Differential Revision: D22053779
fbshipit-source-id: 8da4a651432b453c25e543bc64dbed02946de63d
