Fix conversion error to Expected

[thopre]

Summary

On Ubuntu 18.04 with GCC 7.5 Intel trace code fails to build due to
failure to convert from
lldb_private::process_linux::IntelPTPerThreadProcessTraceUP to
Expected<lldb_private::process_linux::IntelPTPerThreadProcessTraceUP>.
This commit explicitely marks those unique_ptr values as being moved
which fixes the conversion error.

[wallace]

thank you!

I'm surprised the compiler didn't do this automatically

[thopre]

In D126402#3538078, @wallace wrote:

thank you!

I'm surprised the compiler didn't do this automatically

As mentioned, this is GCC 7.5. It might be different with a newer version.

lldb/source/Plugins/Process/Linux/IntelPTCollector.cpp

IntelPTPerThreadProcessTrace::Start(const TraceIntelPTStartRequest &request,
   IntelPTPerThreadProcessTraceUP trace(
       new IntelPTPerThreadProcessTrace(request));
 
   Error error = Error::success();
   for (lldb::tid_t tid : current_tids)
     error = joinErrors(std::move(error), trace->TraceStart(tid));
   if (error)
     return std::move(error);
-  return trace;
+  return std::move(trace);
 }
 
 Error IntelPTCollector::TraceStart(const TraceIntelPTStartRequest &request) {
   if (request.IsProcessTracing()) {
     if (IsProcessTracingEnabled()) {
       return createStringError(
           inconvertibleErrorCode(),
           "Process currently traced. Stop process tracing first");

lldb/source/Plugins/Process/Linux/IntelPTSingleBufferTrace.cpp

#else
 
   if (Expected<PerfEvent> perf_event = PerfEvent::Init(*attr, tid, core_id)) {
     if (Error mmap_err = perf_event->MmapMetadataAndBuffers(buffer_numpages,
                                                             buffer_numpages)) {
       return std::move(mmap_err);
     }
     IntelPTSingleBufferTraceUP trace_up(
         new IntelPTSingleBufferTrace(std::move(*perf_event), initial_state));
-    return trace_up;
+    return std::move(trace_up);
   } else {
     return perf_event.takeError();
   }
 #endif
 }