performance measurements not working on mac

[Emily Bache]

On a mac, the time command doesn't have the flag -o, so if you switch on performance measurement in texttest, it crashes with this message in stderr:

> time: illegal option -- o
> usage: time [-lp] command.

I think this could be solved by altering the command line for example:

http://stackoverflow.com/questions/9388678/how-to-redirect-time-command-output-under-mac-os-x

{ time ls > command.output 2>&1 ; } 2> time.out

I suspect the same trick would work on unix, then you could support both platforms with the same code