[lldb] [lldb-server] Catch and report errors from main loop

[mgorny]

Summary

Catch the possible error from lldb-gdbserver's main loop, and report
it verbosely. Currently, if the loop fails the server exits normally,
rendering the problem indistinguishable from regular termination.

lldb/tools/lldb-server/lldb-gdbserver.cpp

ConnectToRemote(mainloop, gdb_server, reverse_connect, host_and_port,
                   unnamed_pipe, connection_fd);
 
   if (!gdb_server.IsConnected()) {
     fprintf(stderr, "no connection information provided, unable to run\n");
     display_usage(progname, subcommand);
     return 1;
   }
 
-  mainloop.Run();
+  Status ret = mainloop.Run();
+  if (ret.Fail()) {
+    fprintf(stderr, "lldb-server terminating due to error: %s\n",
+            ret.AsCString());
+    return 1;
+  }
   fprintf(stderr, "lldb-server exiting...\n");
 
   return 0;
 }