hashindex: detect mingw byte order

borg/_hashindex.c

@@ -13,10 +13,12 @@
 #endif
 
 #if (defined(BYTE_ORDER)&&(BYTE_ORDER == BIG_ENDIAN)) ||  \
+    (defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)) || \
     (defined(_BIG_ENDIAN)&&defined(__SVR4)&&defined(__sun))
 #define _le32toh(x) __builtin_bswap32(x)
 #define _htole32(x) __builtin_bswap32(x)
 #elif (defined(BYTE_ORDER)&&(BYTE_ORDER == LITTLE_ENDIAN)) || \
+      (defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)) || \
       (defined(_LITTLE_ENDIAN)&&defined(__SVR4)&&defined(__sun))
 #define _le32toh(x) (x)
 #define _htole32(x) (x)