vtest: Add option to catch and return child process exit status

Jakob Bornecrantz requested to merge wallbraker/virglrenderer:vtest-sigchld into main

This commit is based on !108 (merged) and a part of my work to get dEQP/Volt to launch and monitor vtest for crashes as can currently be lost. And a vtest crash is in most cases also a VM crash.

Cheers, Jakob.

Merge request reports