Clean up libcxx-libcxxabi-singlethreaded-x86_64-linux-debian so that it passes the feature flags to lit

http://reviews.llvm.org/D5215


git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@217265 91177308-0d34-0410-b5e6-96231b3b80d8