[CMake] Fix PR23539: Don't reference C++ ABI symbols prior to Mac OS 10.9.

Summary:
This patch implements step 1 from
https://llvm.org/bugs/show_bug.cgi?id=23539#c10

I'd appreciate if you could test it on Mac OS and verify that parts of UBSan
runtime that reference C++ ABI symbols are properly excluded, and fix ASan/UBSan
builds.

Test Plan: regression test suite

Reviewers: thakis, hans

Subscribers: llvm-commits, zaks.anna, kubabrecka

Differential Revision: http://reviews.llvm.org/D10621

llvm-svn: 240617