What about using it as a nickname for the name Malcolm?
Macaulay has a really strong association with Macaulay Culkin - I've never heard it elsewhere, and that's what everyone here would think of.
Cormac also has a negative association, for me, of the guy on Tallifornia. However, in the US, no one I know is familiar with that, so I think outside of Ireland, it's useable.
I'd choose Cormac over Macaulay, largely for the association reasons, but I do actually prefer the name and sound altogether. If you're in a different country, the associations might change.
I really like Macaulay!
I prefer Cormac.