Fix endianness issues in unit test

src/md5.c

@@ -1,21 +1,19 @@
-#include "md5.h"
 #include "arch.h"
+#include "md5.h"
 
 #if defined(MG_ENABLE_MD5) && MG_ENABLE_MD5
 
 static void mg_byte_reverse(unsigned char *buf, unsigned longs) {
-/* Forrest: MD5 expect LITTLE_ENDIAN, swap if BIG_ENDIAN */
-#if BYTE_ORDER == BIG_ENDIAN
-  do {
-    uint32_t t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
-                 ((unsigned) buf[1] << 8 | buf[0]);
-    *(uint32_t *) buf = t;
-    buf += 4;
-  } while (--longs);
-#else
-  (void) buf;
-  (void) longs;
-#endif
+  if (MG_BIG_ENDIAN) {
+    do {
+      uint32_t t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
+                   ((unsigned) buf[1] << 8 | buf[0]);
+      *(uint32_t *) buf = t;
+      buf += 4;
+    } while (--longs);
+  } else {
+    (void) buf, (void) longs;  // Little endian. Do nothing
+  }
 }
 
 #define F1(x, y, z) (z ^ (x & (y ^ z)))