message: [lldb-vscode] Fix dangling pointer in request_evaluate.
  SBError::GetCString() returns a pointer to a string owned by the SBError
  object. The code here was calling GetCString on a temporary and using
  the returned pointer after the temporary was destroyed.
diff: @@ -965,7 +965,10 @@ void request_evaluate(const llvm::json::Object &request) {
  value = frame.EvaluateExpression(expression.data());
  if (value.GetError().Fail()) {
  response["success"] = llvm::json::Value(false);
  - const char *error_cstr = value.GetError().GetCString();
  + // This error object must live until we're done with the pointer returned
  + // by GetCString().
  + lldb::SBError error = value.GetError();
  + const char *error_cstr = error.GetCString();
  if (error_cstr && error_cstr[0])
  EmplaceSafeString(response, "message", std::string(error_cstr));
  else
  