Packager option to not produce a zip file

The packager currently is hard-set to produce a zip file:

https://github.com/awslabs/aws-lambda-cpp/blob/1129e531bae450b6fb78ad5fc08d6222ceb9f68d/packaging/packager#L184-L185

It would be useful to [add an option](https://github.com/awslabs/aws-lambda-cpp/blob/1129e531bae450b6fb78ad5fc08d6222ceb9f68d/packaging/packager#L34) to skip the zipping (which will also make it unnecessary to [have zip](https://github.com/awslabs/aws-lambda-cpp/blob/1129e531bae450b6fb78ad5fc08d6222ceb9f68d/packaging/packager#L54-L57) installed on the packaging system).