Handle internal PL builder JRuby location

The JRuby installation on our internal build infrastructure hides away in a
non-standard path.  This updates our Rakefile to handle that much more smoothly.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Fix build platforms and destinations

This updates our internal build lists to cover the platforms we actually want
packages for.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>