Adds make create-demo-cluster

Based on feedback from new developers to gpdb, we are improving
the top level make targets.

https://github.com/greenplum-db/gpdb/issues/2422

GNUmakefile.in

@@ -152,6 +152,13 @@ installcheck-world:
 installcheck-resgroup:
 	$(MAKE) -C src/test/isolation2 $@
 
+# Create or destory a demo cluster.
+create-demo-cluster:
+	$(MAKE) -C gpAux/gpdemo create-demo-cluster
+
+destroy-demo-cluster:
+	$(MAKE) -C gpAux/gpdemo destroy-demo-cluster
+
 # Run mock tests, that don't require a running server. Arguably these should
 # be part of [install]check-world, but we treat them more like part of
 # compilation than regression testing, in the CI. But they are too heavy-weight

gpAux/gpdemo/Makefile

@@ -27,10 +27,10 @@ export NUM_PRIMARY_MIRROR_PAIRS
 all:
 	$(MAKE) clean
 	$(MAKE) check
-	$(MAKE) cluster
+	$(MAKE) create-demo-cluster
 	$(MAKE) probe
 
-cluster:
+cluster create-demo-cluster:
 	@./demo_cluster.sh
 	@echo ""
 
@@ -42,11 +42,11 @@ check:
 	@./demo_cluster.sh -c
 	@echo ""
 
-clean:
+clean destroy-demo-cluster:
 	@echo "======================================================================"
 	@echo "Deleting cluster.... "
 	@echo "======================================================================"
 	@./demo_cluster.sh -d
 	@echo ""
 
-.PHONY: all cluster probe clean check clean
+.PHONY: all cluster create-demo-cluster probe clean check clean destroy-demo-cluster