Originally committed as 416fa7720e30750939c53935051c6c750dfad2c2
Reverted (due to buildbot failure - breaking lldb) in 7a45aeacf3a23449039ef2efcf476995ae1c7007.
I still can't seem to build lldb locally, but Pavel Labath has kindly
provided a potential fix to preserve the old behavior in lldb by
registering a simple recoverable error handler there that prints to the
desired stream in lldb, rather than stderr.