BIFs: neg_boxed_helper use minimum boxed size (on 32-bit systems)

On 32-bit systems, use `make_maybe_boxed_int64` in `neg_boxed_helper`
since `-(INT32_MAX + 1)` is `INT32_MIN` that fits into a 32-bit boxed
integer.
Before of this change `make_boxed_int64` was used, making a 64-bit boxed
integer for an int32 value.

New `term_compare` implementation will check size and sign metadata before
performing any actual comparison, so all value must be in their "minimal
canonical form".

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

src/libAtomVM/bif.c

@@ -1051,7 +1051,9 @@ static term neg_boxed_helper(Context *ctx, uint32_t fail_label, uint32_t live, t
                     RAISE_ERROR_BIF(fail_label, OVERFLOW_ATOM);
 
                 } else {
-                    return make_boxed_int64(ctx, fail_label, live, -val);
+                    // maybe boxed int64 since we need to handle -(AVM_INT_MAX + 1) that is
+                    // AVM_INT_MIN that fits into a 32 bit boxed value
+                    return make_maybe_boxed_int64(ctx, fail_label, live, -val);
                 }
             }
             #endif