XFAIL TestMachCore for windows hosts

It's been failing since I enabled the test for non-darwin targets. I
made it reference the same bug as the linux core, as it's likely that
the root cause is the same.

llvm-svn: 333401

lldb/packages/Python/lldbsuite/test/functionalities/postmortem/mach-core/TestMachCore.py

@@ -26,6 +26,7 @@ class MachCoreTestCase(TestBase):
         lldb.DBG.SetSelectedPlatform(self._initial_platform)
         super(MachCoreTestCase, self).tearDown()
 
+    @expectedFailureAll(bugnumber="llvm.org/pr37371", hostoslist=["windows"])
     def test_selected_thread(self):
         """Test that the right thread is selected after a core is loaded."""
         # Create core form YAML.