Skip array embedding if MRB_NO_BOXING and MRB_32BIT; fix #4382

On some platforms, `sizeof(mrb_value) > sizeof(void*)*3`, which makes
`MRB_ARY_EMBED_LEN_MAX` zero. And zero sized array cause compile errors.

src/array.c

@@ -1123,8 +1123,14 @@ mrb_ary_clear(mrb_state *mrb, mrb_value self)
   else if (!ARY_EMBED_P(a)){
     mrb_free(mrb, a->as.heap.ptr);
   }
-  ARY_SET_EMBED_LEN(a, 0);
-
+  if (MRB_ARY_EMBED_LEN_MAX > 0) {
+    ARY_SET_EMBED_LEN(a, 0);
+  }
+  else {
+    a->as.heap.ptr = NULL;
+    a->as.heap.aux.capa = 0;
+    ARY_SET_LEN(a, 0);
+  }
   return self;
 }
 

src/value_array.h

@@ -6,6 +6,7 @@
 static inline void
 value_move(mrb_value *s1, const mrb_value *s2, size_t n)
 {
+  if (n == 0) return;
   if (s1 > s2 && s1 < s2 + n)
   {
     s1 += n;

src/vm.c

@@ -1823,7 +1823,7 @@ RETRY_TRY_BLOCK:
         if (kd) regs[len + 1] = kdict;
 
         /* copy mandatory and optional arguments */
-        if (argv0 != argv) {
+        if (argv0 != argv && argv) {
           value_move(&regs[1], argv, argc-mlen); /* m1 + o */
         }
         if (argc < m1) {