stdio-common: Suppress Clang warnings on scanf13.c with fortify enable

stdio-common: Suppress Clang warnings on scanf13.c with fortify enable

clang-19 shows:

scanf13.c:28:40: error: 'sscanf' may overflow; destination buffer in argument 4 has size 8, but the corresponding specifier may require size 11 [-Werror,-Wfortify-source]
   28 |               "A%ms%10ms%4m[bcd]%4mcB", &sp1, &sp2, &sp3, &sp4) != 4)
      |                                               ^
scanf13.c:94:34: error: 'sscanf' may overflow; destination buffer in argument 3 has size 8, but the corresponding specifier may require size 2049 [-Werror,-Wfortify-source]
   94 |   if (sscanf (buf, "%2048ms%mc", &sp3, &sp4) != 2)
      |                                  ^
scanf13.c:110:61: error: 'sscanf' may overflow; destination buffer in argument 4 has size 8, but the corresponding specifier may require size 1501 [-Werror,-Wfortify-source]
  110 |   if (sscanf (buf, "%4mc%1500m[dr/]%548m[abc/d]%3mc", &sp1, &sp2, &sp3, &sp4)
      |                                                             ^
scanf13.c:110:67: error: 'sscanf' may overflow; destination buffer in argument 5 has size 8, but the corresponding specifier may require size 549 [-Werror,-Wfortify-source]
  110 |   if (sscanf (buf, "%4mc%1500m[dr/]%548m[abc/d]%3mc", &sp1, &sp2, &sp3, &sp4)

clang does have some support to handle 'm' prefix for -Wformat; but it
lacks support for -Wfortify to understand that it is up to libc to
allocate the memory, and uses the pointer size instead to calculate
validity.