XCode is a compiler for MacOS. If you run Windows 10, this message should not appear. As Walter asked already: Did you copy files in the prefdir folder from a MacOS installation? But even then modern Matlab version look for a file like "mex_C_win64.xml" and a collision with another preferences file is unlikely.
You can try to re-create the preferences files. Rename (not delete) the preferences folder and try, if the automatic re-creation and a new mex -setup solves the problem. Then you can copy the newly created compiler setup file to the original folder and restore the former preferences folder.
If this does not help, try:
and post the results here.