Always define INSTALL_DDIR and define it such at it contains no extra
/ characters rather than removing them later on.

PR:		conf/178963
Index: Makefile.inc1
===================================================================
--- Makefile.inc1	(revision 250859)
+++ Makefile.inc1	(working copy)
@@ -414,11 +414,12 @@
 INSTALLFLAGS+=	-N ${.CURDIR}/etc
 MTREEFLAGS+=	-N ${.CURDIR}/etc
 .endif
+_INSTALL_DDIR=	${DESTDIR}/${DISTDIR}
+INSTALL_DDIR=	${_INSTALL_DDIR:S://:/:g:C:/$::}
 .if defined(NO_ROOT)
 METALOG?=	${DESTDIR}/${DISTDIR}/METALOG
 IMAKE+=		-DNO_ROOT METALOG=${METALOG}
-INSTALL_DDIR=	${DESTDIR}/${DISTDIR}
-INSTALLFLAGS+=	-U -M ${METALOG} -D ${INSTALL_DDIR:S://:/:g:C:/$::}
+INSTALLFLAGS+=	-U -M ${METALOG} -D ${INSTALL_DDIR}
 MTREEFLAGS+=	-W
 .endif
 .if defined(DB_FROM_SRC) || defined(NO_ROOT)
@@ -1032,7 +1033,7 @@
 	cd ${KRNLOBJDIR}/${INSTALLKERNEL}; \
 	    ${IMAKEENV} ${IMAKE_INSTALL:S/METALOG/kernel.premeta/} \
 	    ${IMAKE_MTREE} PATH=${TMPPATH} ${MAKE} KERNEL=${INSTKERNNAME} \
-	    DESTDIR=${INSTALL_DDIR:S://:/:g:C:/$::}/kernel \
+	    DESTDIR=${INSTALL_DDIR}/kernel \
 	    ${.TARGET:S/distributekernel/install/}
 .if defined(NO_ROOT)
 	sed -e 's|^./kernel|.|' ${DESTDIR}/${DISTDIR}/kernel.premeta > \
@@ -1046,7 +1047,7 @@
 	    ${IMAKEENV} ${IMAKE_INSTALL:S/METALOG/kernel.${_kernel}.premeta/} \
 	    ${IMAKE_MTREE} PATH=${TMPPATH} ${MAKE} \
 	    KERNEL=${INSTKERNNAME}.${_kernel} \
-	    DESTDIR=${INSTALL_DDIR:S://:/:g:C:/$::}/kernel.${_kernel} \
+	    DESTDIR=${INSTALL_DDIR}/kernel.${_kernel} \
 	    ${.TARGET:S/distributekernel/install/}
 	sed -e 's|^./kernel|.|' \
 	    ${DESTDIR}/${DISTDIR}/kernel.${_kernel}.premeta > \