cloud66-oss/habitus: build/builder.go; 12 LoC

Found a possible issue in [cloud66-oss/habitus](https://www.github.com/cloud66-oss/habitus) at [build/builder.go](https://github.com/cloud66-oss/habitus/blob/65812484c945496310e77e3ed92c82f8ef4a5eef/build/builder.go#L122-L133)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first
issue it finds, so please do not limit your consideration to the contents of the below message.

> range-loop variable j used in defer or goroutine at line 125

[Click here to see the code in its original context.](https://github.com/cloud66-oss/habitus/blob/65812484c945496310e77e3ed92c82f8ef4a5eef/build/builder.go#L122-L133)

Click here to show the 12 line(s) of Go which triggered the analyzer.

```go
for j, s := range levels {
b.wg.Add(1)
go func(st Step) {
b.Conf.Logger.Debugf("Step %d - Build for %s", i+j+1, st.Name)
defer b.wg.Done()

err := b.BuildStep(&st, i+j)
if err != nil {
b.Conf.Logger.Fatalf("Build for step %s failed due to %s", st.Name, err.Error())
}
}(s)
}

```

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See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 65812484c945496310e77e3ed92c82f8ef4a5eef