Include SDL_build_config.h without a 'build_config/' prefix

src/SDL_internal.h

@@ -60,7 +60,7 @@
         SDL_free(ptr);               \
     }
 
-#include "build_config/SDL_build_config.h"
+#include "SDL_build_config.h"
 
 #include "dynapi/SDL_dynapi.h"
 

src/dynapi/SDL_dynapi.c

@@ -19,7 +19,7 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
-#include "build_config/SDL_build_config.h"
+#include "SDL_build_config.h"
 #include "SDL_dynapi.h"
 #include "SDL_dynapi_unsupported.h"