DynamoRio null tool crashes on Mozilla Spidermonkey Octane test

Build mozilla-central revision 9bd900888753 and then run the JS octane benchmark in the JS shell under `drrun`. It just crashes. Without `drrun` it will run fine.

```
hg clone -r 9bd900888753 https://hg.mozilla.org/mozilla-central
cd mozilla-central
echo ac_add_options --enable-js-shell > mozconfig
./mach mercurial-setup
./mach build
cd js/src/octane
drrun ../../../obj-*/js/src/js run.js
```

Result: `Segmentation fault (core dumped)`