[Bugpoint] fix use-after-move. NFC
This was flagged in https://www.viva64.com/en/b/0629/ under "Snippet No.
Note that author also states:
"Note that the loop doesn't actually execute at all."
This is not true, but the author can be forgiven; there's two distinct
variables with very similar identifiers:
Reviewers: echristo, srhines, RKSimon
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D62113