I do not think you can affect the way the "Log Viewer" displays the data but if you log the output to a table it will retain the line breaks. On the Job Step properties, Advanced Page, check "Log to Table" and your job output will be written to msdb.dbo.sysjobstepslogs. Be careful though. If you generate a ton of output from your jobs using this table can bloat msdb in a hurry. Just make sure you maintain the job history and indexes on a regular basis.