Fix a bug introduced during the transition to PathV2.

sys::fs::createUniqueFile returns an absolute path, so MakeSharedObject does
too and we don't need to add a './' prefix.

Patch by Jon McLachlan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203931 91177308-0d34-0410-b5e6-96231b3b80d8