Hi,
Welcome to the community!
Do you always get this in your analysis log, regardless of the config value for the report path? If so, then I would wonder whether ${basedir} is being interpolated properly. You can see what property values analysis is getting by appending -Dsonar.scanner.dumpToFile=[path to file] to your analysis command line.
We also have a couple guides that may be useful:
HTH,
Ann