Broken crystal example

I just tried to test oss/crystal-basic example. `PORT=3000 crystal main.cr` works fine locally, `up` deployment works fine:

```
build: 5 files, 3.2 MB (344ms)
deploy: complete (17.647s)
stack: complete (20.219s)
```

But opening result in browser shows:

```
{
message: "Internal server error"
}
```

and in `up logs` I see:

```
12:18:26pm INFO starting name: app-crystal type: server
12:18:26pm INFO found free port 35452 version: $LATEST
12:18:26pm INFO executing "./server" version: $LATEST
12:18:26pm INFO waiting for http://127.0.0.1:35452 version: $LATEST
12:18:26pm ERRO sh: ./server: No such file or directory
```