Fix endianness test on Linux

[ckuethe]

Tested on:

  ckuethe@thorium:~$ uname -a
  Linux thorium 6.6.10-76060610-generic #202401051437~1704728131~22.04~24d69e2 SMP PREEMPT_DYNAMIC Mon J x86_64 x86_64 x86_64 GNU/Linux
  ckuethe@thorium:~$ g++ -E -dM - < /dev/null  | grep -E "ORDER|END"
  #define __ORDER_LITTLE_ENDIAN__ 1234
  #define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__
  #define __ORDER_PDP_ENDIAN__ 3412
  #define __ORDER_BIG_ENDIAN__ 4321
  #define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__

[wcjohns]

Thank you Chris.
Yes, that was definitely a logic inversion on my part.