Had to rename sfml to sfmlbackend because on Windows the filesystem is case insensitive so include <SFML/*> was accidentally including _my_ <sfml/config.hpp> file.

include/guecs.hpp

@@ -8,7 +8,7 @@
 #include <queue>
 #include <typeindex>
 #include <unordered_map>
-#include "sfml/components.hpp"
+#include "sfmlbackend/components.hpp"
 
 namespace guecs {
   using std::shared_ptr, std::wstring, std::string;