pkgix: Export sourced RC-files so that we can accesses them in a `chenv`

This permits using a `chenv` and then `showenv` to see the entire
environment.

Signed-off-by: Marco Elver <me@marcoelver.com>
tests: Update checksum (change in 7c72efd)

Signed-off-by: Marco Elver <me@marcoelver.com>