bug#44674: 28.0.50; Adding current-cpu-time for performance tests

[Eli Zaretskii]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: monnier@iro.umontreal.ca,  mattiase@acm.org,  p.stephani2@gmail.com,
>   44674@debbugs.gnu.org
> Date: Mon, 16 Nov 2020 18:59:28 +0100
> 
> On Nov 16 2020, Eli Zaretskii wrote:
> 
> > Sorry, forgot to answer the 'system' part.  The issue there is whether
> > calling 'system' (and in general waiting for sub-processes to exit) is
> > counted against the process's use of CPU or not.  AFAIK, this is not
> > well defined, either.
> 
> There's times and getrusage.

Right.  I was talking about 'clock', and I proposed to use 'times',
instead for that very reason.  It could also be a more useful feature
to provide user and system time separately, btw.