"The command-line option --no_path_in_file_macros has been added. It removes the path leaving only the filename for the symbols FILE and BASE_FILE." It is defined in the release notes if IAR.
http://supp.iar.com/FilesPublic/UPDINFO/005832/arm/doc/infocenter/iccarm_history.ENU.html
Or you can look for FILE and BASE_FILE macros and remove it you do not want to use the flag.