Fixed building with static Corrade.

Four tests (SceneGraph::Animable, Mesh, MeshTools::Tipsify,
TextureTools::Atlas) however fail, not sure what the cause is, as they
fail somewhere deep long after exiting from main().

src/CMakeLists.txt

@@ -219,9 +219,7 @@ if(BUILD_TESTS)
     add_library(MagnumMathTestLib SHARED
         $<TARGET_OBJECTS:MagnumMathObjects>)
     set_target_properties(MagnumMathTestLib PROPERTIES COMPILE_FLAGS -DCORRADE_GRACEFUL_ASSERT)
-    if(WIN32)
-        target_link_libraries(MagnumMathTestLib ${CORRADE_UTILITY_LIBRARY})
-    endif()
+    target_link_libraries(MagnumMathTestLib ${CORRADE_UTILITY_LIBRARY})
 
     add_library(MagnumTestLib SHARED
         $<TARGET_OBJECTS:MagnumObjects>