Singapore’s state-backed corporate heavyweights – collectively known as “Singapore Inc” – will face tough questions in 2018 on their commitment to the Lion City’s vaunted anti-corruption ethos, observers say, as a shocked public comes to grips with a graft scandal that has engulfed oil rig builder Keppel Corp. One political observer went as far as to describe 2017 as “annus horribilis” for the city state’s corporate sector. That sentiment…