message: fix solver base mixin
diff: @@ -167,7 +167,7 @@ public:
  }
  protected:
  - void set_system_matrix(std::shared_ptr<const MatrixType> system_matrix)
  + void set_system_matrix_base(std::shared_ptr<const MatrixType> system_matrix)
  {
  system_matrix_ = std::move(system_matrix);
  }
  @@ -242,7 +242,7 @@ protected:
  new_system_matrix = gko::clone(exec, new_system_matrix);
  }
  }
  - SolverBase<MatrixType>::set_system_matrix(new_system_matrix);
  + this->set_system_matrix_base(new_system_matrix);
  }
  private:
  