winsim: Build fixes for current mingw64 cross compiles

Change-Id: I5d523a4aa0ca9044b8f83ae6aafd4f3705ff96d6

firmware/target/hosted/sdl/button-sdl.c

@@ -21,6 +21,7 @@
 
 #include <math.h>
 #include <stdlib.h>         /* EXIT_SUCCESS */
+#include <stdio.h>
 #include "sim-ui-defines.h"
 #ifdef HAVE_REMOTE_LCD
 #include "lcd-remote.h"

firmware/target/hosted/sdl/system-sdl.c

@@ -22,6 +22,7 @@
 #include <SDL.h>
 #include <SDL_thread.h>
 #include <stdlib.h>
+#include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
 #ifdef __unix__