test: mark requirement for pthread test

This test explicitly is checking the behaviour of std::thread and
pthread interactions.  This requires pthreads.  Add an appropriate
requirement.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@294903 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/thread/thread.condition/PR30202_notify_from_pthread_created_thread.pass.cpp

@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 //
 // UNSUPPORTED: libcpp-has-no-threads
+// REQUIRES: libcpp-has-thread-api-pthread
 
 // notify_all_at_thread_exit(...) requires move semantics to transfer the
 // unique_lock.