[SPARK-6811] Copy SparkR lib in make-distribution.sh

This change also remove native libraries from SparkR to make sure our distribution works across platforms

Tested by building on Mac, running on Amazon Linux (CentOS), Windows VM and vice-versa (built on Linux run on Mac)

I will also test this with YARN soon and update this PR.

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6373 from shivaram/sparkr-binary and squashes the following commits:

ae41b5c [Shivaram Venkataraman] Remove native libraries from SparkR Also include the built SparkR package in make-distribution.sh