release: Add missing dependencies in the minimal OCI image

The pkg-bootstrap binary depends on fetch.

Approved by:	re
Reviewed by:	cperciva, emaste, bapt
Differential Revision:	https://reviews.freebsd.org/D47661
MFC after:	1 day

(cherry picked from commit ca1f1d2c94)
(cherry picked from commit 4a768794b8)

release/tools/oci-image-minimal.conf

@@ -12,7 +12,10 @@ oci_image_build() {
 			 FreeBSD-runtime \
 			 FreeBSD-certctl \
 			 FreeBSD-kerberos-lib \
+			 FreeBSD-libarchive \
 			 FreeBSD-libexecinfo \
+			 FreeBSD-libucl \
+			 FreeBSD-fetch \
 			 FreeBSD-rc \
 			 FreeBSD-pkg-bootstrap \
 			 FreeBSD-mtree