external: fix build of a test on WinRT with MSVC 2017.

It enables deprecation-warning-is-error by default and the deprecation
warnings in the std::optional compatibility test were not properly
ignored.

src/MagnumExternal/Optional/Test/StdOptionalTest.cpp

@@ -23,6 +23,13 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+/* Needs to be here otherwise the deprecation warning inside OptionalConverter
+   is not ignored */
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable: 4996)
+#endif
+
 #include <memory>
 #include <Corrade/Containers/Optional.h>
 #include <Corrade/TestSuite/Tester.h>
@@ -45,9 +52,6 @@ StdOptionalTest::StdOptionalTest() {
 #ifdef __GNUC__
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#elif defined(_MSC_VER)
-#pragma warning(push)
-#pragma warning(disable: 4996)
 #endif
 void StdOptionalTest::conversion() {
     Debug{} << "Using C++ version" << CORRADE_CXX_STANDARD;
@@ -75,10 +79,12 @@ void StdOptionalTest::conversion() {
 }
 #ifdef __GNUC__
 #pragma GCC diagnostic pop
-#elif defined(_MSC_VER)
-#pragma warning(pop)
 #endif
 
 }}
 
 CORRADE_TEST_MAIN(Magnum::Test::StdOptionalTest)
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif