systemc: Check whether the simulation is running when creating sensitivities.

Change-Id: I499cde0d0eb45ba3287a8719174e1c794c1fb634
Reviewed-on: https://gem5-review.googlesource.com/c/12810
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
2 files changed