package/polkit: add linux-pam as a dependency if linux-pam is selected

Without linux-pam built first, polkit will throw a configuration error:
configure: error: Could not find pam/pam-devel, please install the needed packages.

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>