stage2 提供c后端 提交stage1的测试

stage0/spl_vm.c

@@ -824,7 +824,7 @@ static void spl_vm_sample(spl_vm_t *vm) {
 
     char buf[8192];
     usize len = 0;
-    for (isize i = 0; i < vm->cp; i++) {
+    for (usize i = 0; i < vm->cp; i++) {
         intptr_t s = (intptr_t)vm->frames.data[i].saved_ip;
         if (s <= 0)
             continue;