GCC12: Convert array comparisons to pointer-to-first-element comparis…

…ons.

These are equivalent, but the former is deprecated in C++20 and warned by GCC12.
Refs #60

src/main.c

@@ -860,7 +860,7 @@ int main(void)
     watchdog_init();
 
     /* Relocate DATA. Initialise BSS. */
-    if (_sdat != _ldat)
+    if (&_sdat[0] != &_ldat[0])
         memcpy(_sdat, _ldat, _edat-_sdat);
     memset(_sbss, 0, _ebss-_sbss);