Fix these tests on windows.

It is impossible to create a hard link to a non existing file, so create a
dummy file, create the link an delete the dummy file.

On windows one cannot remove the current directory, so chdir first.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204719 91177308-0d34-0410-b5e6-96231b3b80d8