Port the variadic std::tr1::tuple hack for building gtest for MSVC2012 to ASAN tests.

Summary: This is copied from llvm/utils/unittest/CMakeLists.txt.

Test Plan: This partly enables building ASAN tests with MSVC2012.

Reviewers: timurrrr

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5342

llvm-svn: 217762