[llvm-cov] Handle native paths correctly in the text index

Treat filenames the same way in the text index as we do in the html
index. This is a follow-up to r281008 (an attempt to unbreak the
native_separators.c test on Windows).

Patch by Maggie Yi!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281062 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed