Apple has deep enough pockets. They could stomach it.

There is absolutely no way Apple would build their own foundry. You are talking about a yearly investment of five to ten billion dollars, not to mention how long it'd take to actually make it production ready.

Technical problems aside, Apple's stakeholders would fire the entire board if they approved something like that.

I don’t think shareholders would be very happy to have that money spent on capex instead of paying dividends.

I'm not convinced the advantage it might or might not conter would be worth hundreds of billions of dollars.