Bug 1081242 - Make ASAN's error reporting work while sandboxed on Linux.
Bug 1081242 - On ASAN builds, handle sandbox failure by segfaulting.

The ASAN error reporter will print information about an uncaught SIGSEGV,
but it doesn't care about SIGSYS.  This might get us more information
about sandbox crashes on ASAN builds (which have no crash reporter).