Disable queues_with_libBacktraceRecording

After multiple attempts from both Fred and Adrian, this variant of the
test is still flaky on GreenDragon. This commit disables it while we
continue investigate.

llvm-svn: 359724

lldb/packages/Python/lldbsuite/test/macosx/queues/TestQueues.py

@@ -268,6 +268,7 @@ class TestQueues(TestBase):
             stream.GetData() == "Background",
             "background QoS thread name is valid")
 
+    @skipIfDarwin # rdar://50379398
     def queues_with_libBacktraceRecording(self):
         """Test queues inspection SB APIs with libBacktraceRecording present."""
         exe = self.getBuildArtifact("a.out")