Looking at the MSVC documentation, there are lots of other options that begin with /Z, so I don't think that the right fix is to make a special case for /Zc. Instead I think we should make a special case for /Zi, /ZI and /Z7 and leave other /Z options alone. This was the intention when implementing #1239, but I trusted the issue title too much without checking the docs.

I tested the latest version of this patch on our code base and it worked just fine.

Thanks.