Simplify code with the in place path::native. No functionality change.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190515 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the ASan dll_thunk path

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190516 91177308-0d34-0410-b5e6-96231b3b80d8