If diff file exists but the underlying diff has been fixed, delete the diff file. Change-Id: Icadc21a61c084198a8a246ab6d00a9b885647cde Reviewed-on: https://gem5-review.googlesource.com/12056 Reviewed-by: Gabe Black <gabeblack@google.com> Maintainer: Gabe Black <gabeblack@google.com>