Only possible difference I could see is that the 12-speed chain rings might be infinitesimally narrower than the 11-speed .... but we are talking variances so small that they don't matter.
As others have said, mix-and-match has worked in the past. The only places it might not work would be if you were using a very wide (6-7-8) chain with a much narrower (11-12-speed) cassette, or rear derailleur---and of course MTB systems might have (some certainly do have) different cable-pulls.
Since it is not my money or my ride ... proceed with total confidence.