[tsan] add a run-time-side regression test for https://code.google.com/p/thread-sanitizer/issues/detail?id=40 (tsan-hostile load speculation)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@195325 91177308-0d34-0410-b5e6-96231b3b80d8