build: use runuser(1) instead of setpriv(1)
build: use runuser(1) instead of setpriv(1)

The main difference between both commands is that runuser(1) uses a PAM
session while setpriv(1) does not. From a practical perspective,
runuser(1) is more lenient with environment variables:

  $ sudo setpriv --reuid archie printenv HOME DISPLAY
  /root
  :0:0

  $ sudo setpriv --reuid archie --reset-env printenv HOME DISPLAY
  /home/archie

  $ sudo runuser --pty -u archie printenv HOME DISPLAY
  /home/archie
  :0:0

  $ sudo runuser --pty -u archie -p printenv HOME DISPLAY
  /root
  :0:0

Having both HOME and DISPLAY set allows in particular to use `gpg(1)`
with a graphical pinentry.

AladW/aurutils,AladW/aurutils