Cubs’ trade-deadline shopping list obvious, but do they have prospects necessary to win over sellers?

PITTSBURGH — It’s no secret what the Cubs, clear buyers at the trade deadline, are shopping for this summer. They need pitching. But they won’t be the only team seeking an upgrade. Do they have what it takes to convince sellers to part with their pitchers? “It’s been a really good season so far for our system,” team president Jed Hoyer said a week ago, “position players in particular. We’ve had a lot of real breakouts, which has been good. “That isn’t talking about a desire to trade [away from…