[Tests][Threading] Allow 1‰ error in wait times.

Ideally this should not be an issue and we should always return
strictly *after* the time we waited for.  In practice it can
happen, for mathematics related reasons, that the time isn't
entirely precise, so allow a one thou error.

rdar://163661576

Author: al45tair

unittests/Threading/ConditionVariable.cpp

@@ -67,23 +67,23 @@ TEST(ConditionVariableTest, Timeout) {
     ASSERT_FALSE(ret);
   });
 
-  ASSERT_GE(duration.count(), 0.01);
+  ASSERT_GE(duration.count(), 0.01 * 0.999);
 
   duration = measureDuration([&] {
     ConditionVariable::ScopedLock lock(cond);
     bool ret = cond.wait(0.1s);
     ASSERT_FALSE(ret);
   });
 
-  ASSERT_GE(duration.count(), 0.1);
+  ASSERT_GE(duration.count(), 0.1 * 0.999);
 
   duration = measureDuration([&] {
     ConditionVariable::ScopedLock lock(cond);
     bool ret = cond.wait(1s);
     ASSERT_FALSE(ret);
   });
 
-  ASSERT_GE(duration.count(), 1.0);
+  ASSERT_GE(duration.count(), 1.0 * 0.999);
 
   auto deadline = std::chrono::system_clock::now() + 0.5s;
 
@@ -93,7 +93,7 @@ TEST(ConditionVariableTest, Timeout) {
     ASSERT_FALSE(ret);
   });
 
-  ASSERT_GE(duration.count(), 0.5);
+  ASSERT_GE(duration.count(), 0.5 * 0.999);
 }
 
 // Check that signal() wakes exactly one waiter