[dotest] Remove crashinfo hook

Summary:
This used to be important when all tests were run in a single process,
but that has no longer been the case for a while. Furthermore, this hook fails
to build on new mac versions for several people, and it's not clear
whether fixing it is worth the effort.

Reviewers: jingham, clayborg, davide

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D41871

llvm-svn: 322167