Pass SWAPSIZE in env(1) when invoking mk-vmimage.sh for the

vm-image target, missed in r308737.

Sponsored by:	The FreeBSD Foundation

release/Makefile.vm

@@ -89,7 +89,7 @@ vm-image:
 .if defined(WITH_VMIMAGES) && !empty(WITH_VMIMAGES)
 . for FORMAT in ${VMFORMATS}
 	mkdir -p ${.OBJDIR}/${.TARGET}
-	env TARGET=${TARGET} TARGET_ARCH=${TARGET_ARCH} \
+	env TARGET=${TARGET} TARGET_ARCH=${TARGET_ARCH} SWAPSIZE=${SWAPSIZE} \
 		${.CURDIR}/scripts/mk-vmimage.sh \
 		-C ${.CURDIR}/tools/vmimage.subr -d ${.OBJDIR}/${.TARGET} \
 		-i ${.OBJDIR}/${FORMAT}.img -s ${VMSIZE} -f ${FORMAT} \