[Development] QProcess fork() failure and overcommit

[Ulf Hermann]

> That said, look at the numbers: it increased from ~100 µs to 16.9 ms in the
> worst case. You can't perceive that difference.

This limits the number of processes you can spawn per second to about 60 
(and it goes lower if you eat more RAM). I certainly can notice this 
when using the version of qbs compiled into QtCreator to compile a 
project. In order to keep an 8-core CPU loaded and send extra jobs to 
icecream you need a higher rate.

There is a workaround for that by now, which just uses a separate 
process to spawn the children, but it used to be a problem.

Ulf