Fix MacOS unittest error

Author: hks2002

trantor/utils/crypto/sha1.cc

@@ -40,7 +40,8 @@ A million repetitions of "a"
 #if defined(vax) || defined(ns32000) || defined(sun386) ||                  \
     defined(__i386__) || defined(MIPSEL) || defined(_MIPSEL) ||             \
     defined(BIT_ZERO_ON_RIGHT) || defined(__alpha__) || defined(__alpha) || \
-    defined(__CYGWIN32__) || defined(_WIN64) || defined(_WIN32)
+    defined(__CYGWIN32__) || defined(_WIN64) || defined(_WIN32) ||          \
+    defined(__APPLE__)
 #define BYTE_ORDER LITTLE_ENDIAN
 #endif