system: Have /run/setuid-programs first in $PATH.

Fixes <https://bugs.gnu.org/31814>.
Reported by Clément Lassieur <clement@lassieur.org>.

* gnu/system.scm (operating-system-etc-service)["profile"]: Arrange so
that /run/setuid-programs comes first in $PATH.

gnu/system.scm

@@ -616,9 +616,6 @@ unset PATH
 GUIX_PROFILE=/run/current-system/profile ; \\
 . /run/current-system/profile/etc/profile
 
-# Prepend setuid programs.
-export PATH=/run/setuid-programs:$PATH
-
 # Since 'lshd' does not use pam_env, /etc/environment must be explicitly
 # loaded when someone logs in via SSH.  See <http://bugs.gnu.org/22175>.
 # We need 'PATH' to be defined here, for 'cat' and 'cut'.  Do this before
@@ -645,6 +642,9 @@ do
   fi
 done
 
+# Prepend setuid programs.
+export PATH=/run/setuid-programs:$PATH
+
 # Arrange so that ~/.config/guix/current/share/info comes first.
 export INFOPATH=\"$HOME/.config/guix/current/share/info:$INFOPATH\"