stage2 提供sys包装 解决stage1的bug

stage2/sys/exit.spl

@@ -0,0 +1,22 @@
+// Expect retcode = 6
+
+// exit.spl
+// usage: type exit = @import("exit.spl");  exit.ok();
+
+#extern(vm) fn vm_exit(code: i32);
+
+fn now(code: i32) {
+    vm_exit(code);
+}
+
+fn ok() {
+    vm_exit(0);
+}
+
+fn fail() {
+    vm_exit(1);
+}
+
+fn main(): void {
+    now(6);
+}