Back out "[reland] Skip OpenMP thread when OMP_NUM_THREADS is set to 1"
Summary:
Original commit changeset: 0d5a6537aa2f
build-break
overriding_review_checks_triggers_an_audit_and_retroactive_review
Test Plan: I will watch WhereIsStable
Differential Revision:
D20662253
Ninja: master broken
fbshipit-source-id: 96eb398dd8f4060f85e76fdfdff6aeb2befccc57
