Fix IAR compiler endianness detection in alignment.h

The IAR C/C++ compiler always defines both __LITTLE_ENDIAN__ and __BIG_ENDIAN__ macros internally, assigning '1' to the active endianness and '0' to the inactive one.
The previous check defined(__LITTLE_ENDIAN__) always evaluated to true on IAR, causing big-endian targets to be incorrectly treated as little-endian.

This commit updates the check to verify the value (__XXXX_ENDIAN__ == 1)

Signed-off-by: nzzlinh <dlinhvn@gmail.com>

Author: nzzlinh

ChangeLog.d/fix_iar_endianess.txt

@@ -0,0 +1,2 @@
+Bugfix
+ * Fix incorrect big-endian detection for the IAR compiler in library/alignment.h which caused big-endian targets to be misidentified.

library/alignment.h

@@ -400,10 +400,10 @@ static inline uint64_t mbedtls_bswap64(uint64_t x)
 
 #if !defined(__BYTE_ORDER__)
 
-#if defined(__LITTLE_ENDIAN__)
+#if defined(__LITTLE_ENDIAN__) && (__LITTLE_ENDIAN__ == 1)
 /* IAR defines __xxx_ENDIAN__, but not __BYTE_ORDER__ */
 #define MBEDTLS_IS_BIG_ENDIAN 0
-#elif defined(__BIG_ENDIAN__)
+#elif defined(__BIG_ENDIAN__) && (__BIG_ENDIAN__ == 1)
 #define MBEDTLS_IS_BIG_ENDIAN 1
 #else
 static const uint16_t mbedtls_byte_order_detector = { 0x100 };