WIP: Print output as it's happening

[thibaultduponchelle]

With the current code it first runs the command (make, test_harness, ...) and when it's complete it may 'log' all the output on STDOUT/smokecurrent.log.

What I like more is if the output shows when things are happening instead of needing to wait until the command fully completed.

With this patch that does happen for

• make
• make test_harness

I consider this to be WIP because:
a) Should this behavior be configurable?
b) For _run_harness3_target (and others) it uses a pipe and then
reads from it. I'm guessing that it should be possible to replace
the code with capture (or tee) from Capture::Tiny but I don't
know if that is desirable.
c) On Windows some output is now duplicated in the log because stdout
of make is already logged (see $make_output in sub make_).
d) This is incomplete: only '_run_harness3_target' was updated but
other code has the same structure.
e) It causes the messages (from make, test_harness3) to be logged
without timestamp. Before if the output of make was logged (for
example on Windows) all messages were logged with the same timestamp.
(Ideally each message would have a timestamp of when it happened but
that might not be feasible with Capture::Tiny)

[thibaultduponchelle]

Example of a logfile (on Windows) with these changes: https://perl5.test-smoke.org/logfile/5021750
This (clearly) results in larger log files which I don't know if that is desirable since it will take up more space in the smokedb..