ELF2: Make default-output.s test idempotent.
ELF2: Make default-output.s test idempotent.

This test failed if being run more than once because of the
remaining file of the last run.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@248843 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld