[lldb] TestInferiorCrashing.py should check for crash reason

[bulbazord]

Summary

In a now-reverted series of patches, I inadvertently broke the ability
for lldb-server to explain a crash reason. To ensure that this feature
continues to work after future refactors, let's test the feature.

lldb/test/API/functionalities/inferior-crashing/TestInferiorCrashing.py

def inferior_crashing(self):
         exe = self.getBuildArtifact("a.out")
         self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
 
         self.runCmd("run", RUN_SUCCEEDED)
         # The exact stop reason depends on the platform
         if self.platformIsDarwin():
             stop_reason = 'stop reason = EXC_BAD_ACCESS'
         elif self.getPlatform() == "linux" or self.getPlatform() == "freebsd":
-            stop_reason = 'stop reason = signal SIGSEGV'
+            stop_reason = 'stop reason = signal SIGSEGV: address not mapped to object'
         else:
             stop_reason = 'stop reason = invalid address'
         self.expect("thread list", STOPPED_DUE_TO_EXC_BAD_ACCESS,
                     substrs=['stopped',
                              stop_reason])
 
         # And it should report the correct line number.
         self.expect("thread backtrace all",