Several tests currently deadlock when the lit test suite is run on OS X. Let's mark them as unsupported.
Differential Revision: http://reviews.llvm.org/D14443
llvm-svn: 252402
Even sleep(1) lead to episodical flakes on some machines.
Use an invisible by tsan barrier to enforce required execution order instead.
This makes the tests deterministic and faster.
llvm-svn: 226659