Revert "Fix a build breakage. Looks like the LLVM side of this change has been reverted"

This reverts commit r223375.  We need to use unique_ptr to build with
LLVM r223183.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@223388 91177308-0d34-0410-b5e6-96231b3b80d8