[lldb] avoid assert in threadsanitizer tests on linux

[llunak]

Summary

The tsan tests are unsupported on linux, but they assert in Thread::GetStopDescriptionRaw() because of empty stop reason description. And it is empty because InstrumentationRuntimeTSan::NotifyBreakpointHit() fails to get report from InstrumentationRuntimeTSan::RetrieveReportData(), which is possibly(?) the reason why this is unsupported on linux. Add a dummy stop reason description for this case, which changes the test result from failing to unsupported.

[clayborg]

LGTM, but Kuba should ok this one since he does more ASAN and TSAN stuff.

[kubamracek]

Looks good for get rid of the test failure.

(Although it would we good to actually figure out why RetrieveReportData doesn't work.)

[llunak]

Closing, I forgot to add the "Differential Revision:" line, but D86593 landed sooner anyway.

[teemperor]

Sorry, I totally didn't see this patch (I also only added Fred as a reviewer as he added the assert, so there weren't even any shared reviewers who could have pointed this out).

lldb/source/Plugins/InstrumentationRuntime/TSan/InstrumentationRuntimeTSan.cpp

report->GetObjectForDotSeparatedPath("mops")->GetAsArray()->ForEach(
           addr_t addr =
               o->GetObjectForDotSeparatedPath("address")->GetIntegerValue();
           if (main_address != addr)
             all_addresses_are_same = false;
           return true;
         });
     report->GetAsDictionary()->AddBooleanItem("all_addresses_are_same",
                                               all_addresses_are_same);
+  } else {
+    stop_reason_description = "unknown ThreadSanitizer stop reason";
   }
 
   // Make sure this is the right process
   if (process_sp && process_sp == context->exe_ctx_ref.GetProcessSP()) {
     ThreadSP thread_sp = context->exe_ctx_ref.GetThreadSP();
     if (thread_sp)
       thread_sp->SetStopInfo(
           InstrumentationRuntimeStopInfo::