fix(void): read package payloads through zstd in the install smoke

xbps packages are zstd-compressed. The clean install image had no zstd, so
tar could not list the payload and the smoke failed on a package that was
fine. Install zstd in the install phase.

packaging/void/container-release.sh

@@ -124,7 +124,7 @@ payload_pywhispercpp() {
 phase_install() {
 	: "${PKGS:?}" "${XBPS_VERSION:?}" "${VERSION:?}"
 	[ -d "$XBPS_STAGE/repo" ] && [ -d "$XBPS_STAGE/keys" ] || fail "staged repository or keys are missing"
-	xbps-install -Sy xbps binutils >/dev/null
+	xbps-install -Sy xbps binutils zstd >/dev/null
 
 	echo "== the signed repository is refused while its key is not trusted"
 	# No -y: the documented first sync must not accept an unknown key.