use full hash for hg build id
use full hash for hg build id

Reviewed By: gabelevi

Differential Revision: D15744991

fbshipit-source-id: 5a353895685da9ce0d1f2d0293336c10f73aad0b

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow