(u)intmax_t is (unsigned) long on FreeBSD mips64.  This corrects the
bizzare error:

error: format specifies type
      'uintmax_t' (aka 'unsigned long long') but the argument has type
      'uintmax_t' (aka 'unsigned long') [-Werror,-Wformat]
                printf("  Len: %ju\n", (uintmax_t)sb->sb_sandboxlen);
                               ~~~     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                               %ju