…k flag

Summary: /Zc:dllexportInlines with /fallback may cause unexpected linker error. It is better to disallow compile rather than warn for this combination.

Reviewers: hans, thakis

Reviewed By: hans

Subscribers: cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D54426

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@346733 91177308-0d34-0410-b5e6-96231b3b80d8