[ASan/Win tests] Remove the extra 'cat' in front of FileCheck now that it's clear we should use GnuWin32 rather than Cygwin on the PATH on Windows (see PR19744)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@209622 91177308-0d34-0410-b5e6-96231b3b80d8