osbuilder: Build Skopeo, umoci, attestation-agent

When the environment variable $SKOPEO_UMOCI is set to "yes", Skopeo and
umoci are built inside the guest build container and installed to the
guest rootfs. The respective build- and runtime dependencies are added.
This respects the (existing) $LIBC variable (gnu/musl) and avoids issues
with glibc mismatches.
This is currently only supported for Ubuntu guests, as the system Golang
packages included in the versions of other distros that we use are too
old to build these packages, and re-enabling installing Golang from
golang.org is cumbersome, given especially that it is unclear how long
we will keep using Skopeo and umoci.

Additionally, when the environment variable $AA_KBC is set,
attestation-agent (with that KBC) is included.

This replaces some logic in ccv0.sh that is removed.

Fixes: #2907
Signed-off-by: Jakob Naucke <jakob.naucke@ibm.com>

tools/osbuilder/scripts/lib.sh

@@ -219,6 +219,25 @@ ${extra}
 	  agent-is-init-daemon: "${AGENT_INIT}"
 EOT
 
+	if [ "${SKOPEO_UMOCI}" = "yes" ]; then
+		cat >> "${file}" <<-EOF
+	skopeo:
+	  url: "${skopeo_url}"
+	  version: "${skopeo_branch}"
+	umoci:
+	  url: "${umoci_url}"
+	  version: "${umoci_tag}"
+EOF
+	fi
+
+	if [ -n "${AA_KBC}" ]; then
+		cat >> "${file}" <<-EOF
+	attestation-agent:
+	  url: "${attestation_agent_url}"
+	  kbc: "${AA_KBC}"
+EOF
+	fi
+
 	local rootfs_file="${file_dir}/$(basename "${file}")"
 	info "Created summary file '${rootfs_file}' inside rootfs"
 }