[Support] Quote arguments containing \n on Windows

Fixes at_file.c test failure caused by r341988. We may want to change
how we treat \n in our tokenizer, but this is probably a good fix
regardless, since we can invoke all kinds of programs with different
interpretations of the command line quoting rules.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341992 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed