Patched to compile on OpenBSD.

src/dynapi/SDL_dynapi.c

@@ -220,7 +220,7 @@ static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
     }
     return retval;
 }
-#elif defined(unix) || defined(__APPLE__)
+#elif defined(unix) || defined(__unix__) || defined(__APPLE__)
 #include <dlfcn.h>
 static SDL_INLINE void *get_sdlapi_entry(const char *fname, const char *sym)
 {