Fail repo builds that encounter assembler errors
Summary: We fatal production builds when we encounter verification errors after compilation or optimization, but we silently generate fatal units for assembler errors, hackc errors (places the `failwith` assertion is used), and any transient or configuration based system errors (e.g. failures during IPC between hackc and hhvm).
Reviewed By: ricklavoie, jano, alexeyt
Differential Revision:
D20967480
fbshipit-source-id:
f974ccb37d3b8612daa7f0f71318da107a7ea353