vmimage.subr: Enable FreeBSD-base repo if pkgbase

When creating a VM image using pkgbase, create a configuration file in
/usr/local/etc/pkg/repos/FreeBSD.conf which enables the FreeBSD-base
repository.  (This repository is defined in /etc/pkg/FreeBSD.conf as
being disabled by default.)

Reported by:	Mark Millard
MFC after:	immediately (needed for 15.0-RC1)

release/tools/vmimage.subr

@@ -107,6 +107,10 @@ vm_install_base() {
 		selected=$(vm_base_packages_list | vm_extra_filter_base_packages)
 		$pkg_cmd install -U -r FreeBSD-base $selected
 		metalog_add_data ./var/db/pkg/local.sqlite
+		mkdir -p ${DESTDIR}/usr/local/etc/pkg/repos
+		echo 'FreeBSD-base: { enabled: yes }' > ${DESTDIR}/usr/local/etc/pkg/repos/FreeBSD.conf
+		metalog_add_data /usr/local/etc/pkg/repos
+		metalog_add_data /usr/local/etc/pkg/repos/FreeBSD.conf
 	else
 		cd ${WORLDDIR} && \
 			make DESTDIR=${DESTDIR} ${INSTALLOPTS} \