"codedescriptor.dmr" is an artifact file that is created in the "model_xxxxx_rtw" code generation folder for targets such as ert.tlc or slrealtime.tlc. The file is used by Simulink in subsequent (re-)build processes. If you are not encountering any adverse behavior, I think you can simply ignore these warnings.
You can try to remove the warning by running the following commands to reset your MATLAB path:
>> restoredefaultpath
>> rehash toolboxcache
Re-run the build. If this resolved the issue, save the new settings by executing:
>> savepath
Hope it helps!!
