php: fix phar script packaging

Fix several issues with how the phar package is installed and packaged:
* The symlink was pointing to an absolute path on the host, which
  naturally does not work on the target
* The script itself had a shebang pointing to a path on the host
* A file-rdeps warning was occurring due to rpmdeps detecting that the
  script requires the php binary; in order to prevent the main php
  package depending on php-cli which provides the php binary, move the
  phar script to its own package (I suspect most people won't need it
  anyway).

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>