cmake: fix the compiler-rt build with MSVC

This sets flags and excludes things that aren't working with MSVC yet,
allowing us to build the ASan runtime as part of the cmake build.

Differential Revision: http://llvm-reviews.chandlerc.com/D1525

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@189304 91177308-0d34-0410-b5e6-96231b3b80d8