It's really not. At least at large organizations, it is taken for granted that anyone you hire will pass the bar exam. It doesn't factor into the hiring decision at all.
Most large firms draw their entry-level associates from their pool of summer interns, which they hire two years before they graduate law school and take the bar exam. They also usually give people a mulligan on failing the bar exam the first time, so people might work somewhere for 6+ months before passing the bar.