Even it is an unknow exception for GDB, we still can try to cast it to std::exception and print some information from `what()`. Change-Id: Ie0cdc978eb1b3e130bc2153eae99025dcd0109f7 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48825 Reviewed-by: Gabe Black <gabe.black@gmail.com> Maintainer: Gabe Black <gabe.black@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com>