Prefer use of __MINGW_PRINTF/SCANF_FORMAT if available.

Mingw headers sometimes like to define alternative scanf/printf
format attributes depending on whether they're using clang, UCRT,
MINGW_ANSI_STDIO, or the microsoft version of printf/scanf.  This
change attempts to use the right one on the given platform.

This is an attempt to fix part of #40355.

src/lib/string/printf.c

@@ -8,9 +8,9 @@
  * \brief Compatibility wrappers around snprintf and its friends
  **/
 
+#include "lib/cc/torint.h"
 #include "lib/string/printf.h"
 #include "lib/err/torerr.h"
-#include "lib/cc/torint.h"
 #include "lib/malloc/malloc.h"
 
 #include <stdlib.h>
@@ -45,7 +45,7 @@ tor_vsnprintf(char *str, size_t size, const char *format, va_list args)
     return -1; /* no place for the NUL */
   if (size > SIZE_T_CEILING)
     return -1;
-#ifdef _WIN32
+#if defined(_WIN32) && !defined(HAVE_VSNPRINTF)
   r = _vsnprintf(str, size, format, args);
 #else
   r = vsnprintf(str, size, format, args);