bin: normalize paths using SRCTOP-relative paths or :H when possible

This simplifies make logic/output

MFC after:	1 month
Sponsored by:	Dell EMC Isilon

bin/csh/Makefile

@@ -9,7 +9,7 @@
 .include <src.opts.mk>
 
 PACKAGE=runtime
-TCSHDIR= ${.CURDIR}/../../contrib/tcsh
+TCSHDIR= ${SRCTOP}/contrib/tcsh
 .PATH: ${TCSHDIR}
 
 PROG=	csh

bin/df/Makefile

@@ -2,7 +2,7 @@
 # $FreeBSD$
 
 PACKAGE=runtime
-MOUNT=	${.CURDIR}/../../sbin/mount
+MOUNT=	${SRCTOP}/sbin/mount
 .PATH: ${MOUNT}
 
 PROG=	df

bin/freebsd-version/Makefile

@@ -4,7 +4,7 @@ PACKAGE=runtime
 SCRIPTS = freebsd-version
 MAN = freebsd-version.1
 CLEANFILES = freebsd-version freebsd-version.sh
-NEWVERS = ${.CURDIR}/../../sys/conf/newvers.sh
+NEWVERS = ${SRCTOP}/sys/conf/newvers.sh
 
 freebsd-version.sh: ${.CURDIR}/freebsd-version.sh.in ${NEWVERS}
 	eval $$(egrep '^(TYPE|REVISION|BRANCH)=' ${NEWVERS}) ; \

bin/rmail/Makefile

@@ -2,7 +2,7 @@
 # $FreeBSD$
 
 PACKAGE=sendmail
-SENDMAIL_DIR=${.CURDIR}/../../contrib/sendmail
+SENDMAIL_DIR=${SRCTOP}/contrib/sendmail
 .PATH:	${SENDMAIL_DIR}/rmail
 
 # Not much point this being static. It calls a shared sendmail...

bin/sh/Makefile

@@ -28,9 +28,9 @@ WARNS?=	2
 WFORMAT=0
 
 .PATH:	${.CURDIR}/bltin \
-	${.CURDIR}/../kill \
-	${.CURDIR}/../test \
-	${.CURDIR}/../../usr.bin/printf
+	${.CURDIR:H}/kill \
+	${.CURDIR:H}/test \
+	${SRCTOP}/usr.bin/printf
 
 CLEANFILES+= mknodes mknodes.o \
 	mksyntax mksyntax.o