Use GNU time to record maximum resident set size in addition to elapsed time

[Gbury]

It is very convenient that currently benchpress records the time for each prover run, but it would be even more useful to also have an estimation of the memory used by each process. Fortunately, the GNU time utility provide such a fonctionality.

Something to that effect could be obtained by wrapping the prover calls like this:

/usr/bin/time -f "%e\n%M" -o some_tmp_file prover_cmd_to_run....

And then reading the temporary file for the output of time (%e is for the elapsed real time in seconds, and %M the maximum resident set size in Kbytes).