message: fix test_install warnings
diff: @@ -122,7 +122,8 @@ int main(int, char **)
  // core/base/mtx_io.hpp
  {
  - /*auto test =*/gko::layout_type::array;
  + static_assert(gko::layout_type::array != gko::layout_type::coordinate,
  + "mtx_io.hpp not included properly!");
  }
  // core/base/name_demangling.hpp
  @@ -134,7 +135,8 @@ int main(int, char **)
  // core/base/polymorphic_object.hpp
  {
  - /*auto test =*/gko::layout_type::array;
  + gko::PolymorphicObject *test;
  + (void)test; // silence unused variable warning
  }
  // core/base/range.hpp
  @@ -161,12 +163,13 @@ int main(int, char **)
  // core/base/std_extensions.hpp
  {
  static_assert(std::is_same<gko::xstd::void_t<double>, void>::value,
  - "std::extensions.hpp not included properly!");
  + "std_extensions.hpp not included properly!");
  }
  // core/base/types.hpp
  {
  - /*auto test =*/gko::size_type{12};
  + static_assert(gko::size_type{12} == 12,
  + "types.hpp not included properly");
  }
  // core/base/utils.hpp
  