The Empowered Spell metamagic option says:
When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.
You can use Empowered Spell even if you have already used a different Metamagic option during the casting of the spell.
The Wild Magic sorcerer's 18th-level feature, Spell Bombardment, says (PHB, p. 103):
Beginning at 18th level, the harmful energy of your spells intensifies. When you roll damage for a spell and roll the highest number possible on any of the dice, choose one of those dice, roll it again and add that roll to the damage. You can use the feature only once per turn.
Suppose we have an 18th-level wild magic sorcerer, and suppose that he has a Charisma modifier of at least +2. He casts fire bolt, hits, and rolls a 1 on the d10 for damage (let's ignore the rest of the dice). Expending a single sorcery point, he empowers the spell and rerolls the die. This time, it's a 10. Our sorcerer now uses Spell Bombardment to get an extra d10 of damage. This one is a 1 as well. Does the Empower Spell from before allow him to reroll this second die as well?