There is no std::errc::success, remove the llvm one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209960 91177308-0d34-0410-b5e6-96231b3b80d8
Fix windows build.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209961 91177308-0d34-0410-b5e6-96231b3b80d8
really fix the windows build.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209964 91177308-0d34-0410-b5e6-96231b3b80d8