clean(warnings): fix "MIN" redefined warning

Some platforms, like Zephyr, already define MIN and definition in WAMR cause
`warning: "MIN" redefined` warning.
Check if it was defined before, and do not redefine it.

Signed-off-by: Krisztian Szilvasi <34309983+kr-t@users.noreply.github.com>

Author: kr-t

core/iwasm/libraries/lib-wasi-threads/tid_allocator.c

@@ -8,7 +8,10 @@
 #include "bh_log.h"
 
 bh_static_assert(TID_MIN <= TID_MAX);
+/* Some platforms, like Zephyr, have already defined MIN at this point */
+#ifndef MIN
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#endif
 
 bool
 tid_allocator_init(TidAllocator *tid_allocator)