add shellspec golden harness for the legacy make engine

- spec/golden/cases.txt: 69 black-box cases (CLI wrapper mode and make
  include mode) run in a hermetic sandbox with a mocked docker
- spec/golden/expected/*.txt recorded from this engine (baseline)
- make test / test-golden / golden-record / lint dev targets

spec/fixtures/host-project/stack/host/fabio.yml

@@ -0,0 +1,13 @@
+services:
+  fabio:
+    image: fabiolb/fabio:1.6.3
+    container_name: ${HOST_COMPOSE_PROJECT_NAME:-localhost}-fabio
+    depends_on: [consul]
+    ports:
+      - "80:80"
+      - "443:443"
+    environment:
+      FABIO_REGISTRY_CONSUL_ADDR: ${DOCKER_HOST_INET4:-127.0.0.1}:8500
+      FABIO_LOG_ACCESS_TARGET: ${HOST_FABIO_LOG_ACCESS:-}
+    networks:
+      - public