[clang-cl] /Z7 now generates normal debug info, not just line info

Previously LLVM could not process any debug info we produced, so it
didn't make sense to spend time generating it. Now that it has primitive
support for local variable info, it does make sense to generate normal
debug info.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@260435 91177308-0d34-0410-b5e6-96231b3b80d8