Clients are required to make this call prior to destroying the object. Adding
the missing call fixes an assertion that was triggering at program termination
time in the LLJITWithExecutorProcessControl example.
Two typos, one unsused include and some leftovers from the TargetProcessControl -> ExecutorProcessControl renaming
Reviewed By: xgupta
Differential Revision: https://reviews.llvm.org/D110260