add --exec-prefix=/ to psmisc

[gerard@…]

rationale from Matthias Benkmann:

I wonder if we should not add the switch --exec-prefix=/ to the configure for psmisc. I think the tools from psmisc should be available even when /usr is not mounted. After all, sysvinit's killall and pidof are also on the / partition. And fuser is a tool someone might need for troubleshooting even if /usr is not mounted. Let's say I run umount -a and one partition can't be unmounted because it's busy. I would need fuser to find out who's the culprit but chances are that umount -a just unmounted the /usr partition (unless that was the busy partition).

[gerard@…]

Done