`nimble run` should expose the exit code of the target
When running `nimble run` with a binary package, the exit code of the program is lost, and is always 0.

Example:

- `nimble init test`
    - Follow steps to create a binary package
- `cd test`
- ```
    cat << EOF > src/test.nim
    echo "Hello, world"
    quit(1)
    EOF
    ```
- `nimble run`
- `echo $?`

Exit code is 0, output is:

```
  Verifying dependencies for test@0.1.0
   Building test/test using c backend
Hello, world
```

I can see 2 options:

1. Have `nimble run` use the same exi coe as the target being ran
2. Have Nimble output the exit code to stderr if it is not 0

I would prefer option 1 personally.