Simplify memory management with std::unique_ptr.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211538 91177308-0d34-0410-b5e6-96231b3b80d8
Fix cmake build.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211539 91177308-0d34-0410-b5e6-96231b3b80d8