r267556 made backslashes escape the next character
unconditionally in rsp files.  This test echos a path into
a rsp file, and paths contain backslashes on Windows. Since
it's not important for this test to get the filename from
the rsp file, just pass it regularly.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@267601 91177308-0d34-0410-b5e6-96231b3b80d8