lit.py: Fix new test harder for systems that don't use / as os.path.sep

I didn't think about '%{inputs}' having the same problem. This one
should be a fully Windows path name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315779 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed