[lldb/Test] Use self.assertIn in TestGdbRemoteTargetXmlPacket

On the ARM buildbot the returned architecture is `armv8l` while
getArchitecture() just returns `arm`.

Author: JDevlieghere

lldb/test/API/tools/lldb-server/registers-target-xml-reading/TestGdbRemoteTargetXmlPacket.py

@@ -43,7 +43,7 @@ def test_g_target_xml_returns_correct_data(self):
 
         architecture = root.find("architecture")
         self.assertIsNotNone(architecture)
-        self.assertEqual(architecture.text, self.getArchitecture())
+        self.assertIn(self.getArchitecture(), architecture.text)
 
         feature = root.find("feature")
         self.assertIsNotNone(feature)