[Reproducer] Enable crash reports for reproducer tests

For some reason the reproducer tests seem really proficient at
uncovering structural issues in LLDB related to how we tear down things,
but of course only on the bots.

The pretty stack trace helps a bit, but what I really want is the crash
reports which contain much more information, such as what other threads
we doing.

Crash reports are automatically suppressed by lit. This patch
(temporarily) disables that for the reproducer tests.