Collect exit status of (aplay) commands started in the background #702

Many (most?) tests start aplay or other commands in the background. Either because they start several of them concurrently or because they need to perform some action while aplay is running. It is possible to collect the exit status of these commands yet this is almost never done.

The fix is generally simple and looks like this:

timeout --kill-after 5  21 aplay --duration 20  ... & aplayPID1=$!
timeout --kill-after 5  21 aplay --duration 20 ... & aplayPID2=$!
sudo timeout --kill-after 5 --preserve-status 4 sof-logger ... & loggerPID=$!
...
wait "$aplayPID1" || die "aplay failed..."
wait "$loggerPID" || die "logger failed..."

A for loop can be implemented with some $aplayPID[@] bash array.

This is also a better way to make sure "rogue" processes don't pollute the next test, I mean better than a blind "killall aplay"

Related to other green failure issues set -e #312 and aplay --fatal-errors #489

cc:

• [sof-test] add set -e to all test cases (Unless You Love Debugging) #312
• Use aplay --fatal-errors to stop on underruns or errors #489