ERROR ITMS-90087: “Unsupported Architecture. Your executable contains unsupported architecture ‘[x86_64, i386]’.”

This means it’s time to get rid of i386 code, presumably within one of your dylib files. Open a terminal and issue the following:

lipo -remove i386 yourlib.dylib -o yourlib_fixed.dylib

Now you can preferably delete the old dylib and rename to new one to match your old dylib’s name. Either way, replace the old dylib with the new one and resubmit your app.