for Visual Studio, and is a bit of a pain when you want to include the
LLVM headers from your own project, so I moved the check a bit down into
the Unix case to avoid the hassle... Here is a patch
Patch by Morten Ofstad!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17450 91177308-0d34-0410-b5e6-96231b3b80d8
5200ad1b34