Release binaries are unnecessarily large

[stuarteberg]

The Linux binary distribution tarball (and possibly the Mac one, too) is larger then it ought to be. That's mostly because we don't prune out the unnecessary .so files, nor do we prune out .a files (which are all unnecessary).

It wouldn't be very hard to write a short script to analyze the dvid binary and its shared object dependencies (recursively). It should be called from make-release-distribution.sh.