We do not support /etc/pam.d directory.
See https://www.illumos.org/issues/2947

--- cups-2.4.7/config-scripts/cups-pam.m4.orig	2023-10-25 19:36:00.681132879 +0200
+++ cups-2.4.7/config-scripts/cups-pam.m4	2023-10-25 19:36:23.527933638 +0200
@@ -43,14 +43,6 @@
 	], [
 	    PAMLIBS="-lpam"
 	])
-
-	# Find the PAM configuration directory, if any...
-	for dir in /private/etc/pam.d /etc/pam.d; do
-	    AS_IF([test -d $dir], [
-		PAMDIR="$dir"
-		break;
-	    ])
-	done
     ])
 
     LIBS="$SAVELIBS"