Thank you Rene,
Could you please elaborate on what is the problem with outputting the task before it starts in the context of parallel action execution - the issue is not trivial for me.
About the flushing - it make sense. There are though ways this to be resolved. First, if the flushing behavior is optional you can use the current output behavior in the automated environments (where usually computer interpretation is involved).
About the human readability - since the humans that will use the option will most probably be the same humans that will need to read it - it will be up to them to decide is it readable enough to worth the immediate response or not. There also several things that could be than to make it easier - for example msvc prefixes the outputs from different threads with a different id (this also could make the impossibility of parsing the result not so hard task). The flushes could be made on chunks (for sure they need to be at least line by line). Probably a variable on target that specifies a regular expression(s) that determine the flushing points will be a good feature.
Having immediate flushing when -j1 is a very good idea.
Thanks,
George