CRASH in 32-bit signal_racesys test

http://dynamorio.org/CDash/testDetails.php?test=153499&build=14701

Test: code_api|linux.signal_racesys (Failed)
Build: release-external-32 (ARM.Ubuntu1404.gcc484.CAM) on 2016-11-16 05:16:41
Repository revision: c3bd1ca94176c56dff60880ffff3d151061a21ff

```
Exit Value 139
Fail Reason Required regular expression not found.Regex=[^all done
$
]

Test output
```

Looks like a SIGSEGV not reported by DR? That would have to be early, or
late after the "all done" which is not printed...unclear how this can happen.

Start with the code_api|linux.signal_racesys test and its CDash failure for the release-external-32 ARM.Ubuntu1404.gcc484.CAM build. Reproduce the exit value 139 and inspect whether the SIGSEGV occurs before or after the expected "all done" output; done means identifying the cause and making the test complete with its required output.

Written by the indexing model from the issue text.