fix unmarshalling bit sets in json

Fixes #4761

core/encoding/json/unmarshal.odin

@@ -117,9 +117,25 @@ assign_int :: proc(val: any, i: $T) -> bool {
 	case uint:    dst = uint   (i)
 	case uintptr: dst = uintptr(i)
 	case:
+		is_bit_set_different_endian_to_platform :: proc(ti: ^runtime.Type_Info) -> bool {
+			if ti == nil {
+				return false
+			}
+			t := runtime.type_info_base(ti)
+			#partial switch info in t.variant {
+			case runtime.Type_Info_Integer:
+				switch info.endianness {
+				case .Platform: return false
+				case .Little:   return ODIN_ENDIAN != .Little
+				case .Big:      return ODIN_ENDIAN != .Big
+				}
+			}
+			return false
+		}
+
 		ti := type_info_of(v.id)
-		if _, ok := ti.variant.(runtime.Type_Info_Bit_Set); ok {
-			do_byte_swap := !reflect.bit_set_is_big_endian(v)
+		if info, ok := ti.variant.(runtime.Type_Info_Bit_Set); ok {
+			do_byte_swap := is_bit_set_different_endian_to_platform(info.underlying)
 			switch ti.size * 8 {
 			case 0: // no-op.
 			case 8: