fix an issue where function call args were being passed backwards

test.comet

@@ -1,12 +1,12 @@
 struct Foo {
     int x
 
-    init() {
-        self.x = 123
+    init(int x) {
+        self.x = x
     }
 }
 
 func main() -> int {
-    Foo x = new Foo()
+    Foo x = new Foo(4)
     return x.x
 }

vm_src/vm.c

@@ -132,8 +132,8 @@ void callFunction(CometVM* vm, CometSerializedFunc* function) {
     callFrame->sp = 0;
     callFrame->funcName = function->name;
 
-    for (size_t i = 0; i < function->numArgs; i++) {
-        callFrame->args[i] = pop(vm);
+    for (size_t i = function->numArgs; i > 0; i--) {
+        callFrame->args[i - 1] = pop(vm);
     }
 
     vm->callStack[vm->callIdx] = callFrame;