[CBRD-25525] Modify cub_vsnprintf() to support vsnprintf() in Windows…

… build (#5409) : to release/11.3 (#5421)

http://jira.cubrid.org/browse/CBRD-25525

Match the return value of vsnprintf() function and cub_vsnprint() of Windows version.
vsnprintf() is supported in Windows, but other functions also call mapped functions, so the existing method is maintained.
backport [CBRD-25525] Modify cub_vsnprintf() to support vsnprintf() in Windows build #5409

src/base/porting.c

@@ -1476,6 +1476,11 @@ cub_vsnprintf (char *buffer, size_t count, const char *format, va_list argptr)
 {
   int len = _vscprintf_p (format, argptr) + 1;
 
+  if (count == 0)
+    {
+      return (len - 1);
+    }
+
   if (len > (int) count)
     {
       char *cp = (char *) malloc (len);
@@ -1495,7 +1500,7 @@ cub_vsnprintf (char *buffer, size_t count, const char *format, va_list argptr)
       buffer[count - 1] = 0;
 
       free (cp);
-      return (int) count;
+      return (int) len;
     }
 
   return _vsprintf_p (buffer, count, format, argptr);