Use SRCTOP-relative paths to other directories instead of .CURDIR-relative ones

This implifies pathing in make/displayed output

MFC after:	3 weeks
Sponsored by:	Dell EMC Isilon

lib/libpam/modules/Makefile.inc

@@ -1,11 +1,11 @@
 # $FreeBSD$
 
-PAMDIR=		${.CURDIR}/../../../../contrib/openpam
+PAMDIR=		${SRCTOP}/contrib/openpam
 
 MK_INSTALLLIB=	no
 MK_PROFILE=	no
 
-CFLAGS+= -I${PAMDIR}/include -I${.CURDIR}/../../libpam
+CFLAGS+= -I${PAMDIR}/include -I${SRCTOP}/lib/libpam
 
 SHLIB_NAME?=	${LIB}.so.${SHLIB_MAJOR}
 LIBADD+=	pam

lib/libpam/modules/pam_passwdqc/Makefile

@@ -1,6 +1,6 @@
 # $FreeBSD$
 
-SRCDIR=	${.CURDIR}/../../../../contrib/pam_modules/pam_passwdqc
+SRCDIR=	${SRCTOP}/contrib/pam_modules/pam_passwdqc
 .PATH: ${SRCDIR}
 
 LIB=	pam_passwdqc

lib/libpam/modules/pam_ssh/Makefile

@@ -1,7 +1,7 @@
 # PAM module for SSH
 # $FreeBSD$
 
-SSHDIR=	${.CURDIR}/../../../../crypto/openssh
+SSHDIR=	${SRCTOP}/crypto/openssh
 
 LIB=	pam_ssh
 MAN=	pam_ssh.8