Failed build-deps returns zero status code

[vzaharee]

When a build-deps fails, such as when it is unable to resolve a Maven sub-dependency when building a voom dependency, the process exits with a zero status code.

This appears to be the culprit: https://github.com/LonoCloud/lein-voom/blob/master/src/leiningen/voom.clj#L436-L438

This also appears to mean that lein voom will continue working even though a recursive build-deps has failed: https://github.com/LonoCloud/lein-voom/blob/master/src/leiningen/voom.clj#L333