Why would attorney-client privilege come into it? Trump just publicly said he didn't send Rudy to Ukraine - here's the relevant part of the transcript (and by 'transcript' I mean an actual word-for-word record of one criminal pervert talking to another criminal pervert, and not any sort of summary memorandum):
Bill O'Reilly: "I don't really care what he says, but what was Rudy Giuliani doing in Ukraine on your behalf?"
Trump: "Well, you have to ask that to Rudy, but Rudy, I don't, I don't even know. I know he was going to go to Ukraine and I think he canceled a trip. But, you know, Rudy has other clients other than me. I'm one person."
Bill O'Reilly: "So, you didn't direct him to go there on your behalf?"
Trump: "No, but but you have to understand, Rudy is a great corruption fighter. He's one of the greatest in the last 50 years. He was the greatest mayor in the history of the city of New York, by far, much better than Bloomberg. I mean, Bloomberg when he took it over, the crime was in great shape. I mean, Rudy did a great job as mayor.
"You know, when you think, I mean, he has to look, I mean, he felt, he felt personally insulted by what happened during my campaign because there were a lot of bad things happening and you know that better than anybody else. A lot of really bad things were happening during my campaign. In a way, it's a miracle that I won because with all of those horrible things with the media against, with the the dishonesty, the tremendous dishonesty.
"Then you hear about Google and Facebook and Twitter, everybody against and we won. I guess you could say it was a landslide in the Electoral College."
And in any case, it's not like Giuliani was working for Trump - Rudy says Trump wasn't paying him, he was getting paid from money-laundering Russian oligarchs and he was getting paid by an expat Venezuelan money-laundering oligarch, and used to be paid by a money-laundering(pdf link) Qatari Sheik Abdullah Bin Khalid al-Thani (who is believed to have sheltered 9/11 mastermind Khalid Sheik Mohammed)... there's a long list of people who paid Rudy Giuliani, and it's made of up financial criminals, terrorist sympathizers, and resource-looting oligarchs (as opposed to the West's capitalist UHNWIs or China's neo-feudal mandarins) - who are, by what is doubtless sheer coincidence, the same class of people (in many cases, the same exact people, such as Russian-Ukranian oligarch (and wanted embezzeler ) Pavel Fuks) whom Donald Trump does business with.