procps-ng: add INSTALL_STAGING=YES

Procps-ng libraries needed in the staging directory by
the new package openvmtools.

Signed-off-by: Karoly Kasza <kaszak@gmail.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>