feat: generalize container tool usage in bundle build target

Author: rhuss

changelog/fragments/generalize-container-tool.yaml

@@ -0,0 +1,5 @@
+entries:
+  - description: >
+      The bundle build target now respects the CONTAINER_TOOL variable, allowing users to use alternative container tools like podman instead of docker.
+    kind: "change"
+    breaking: false 

internal/plugins/manifests/v2/init.go

@@ -241,7 +241,7 @@ bundle: kustomize operator-sdk ## Generate bundle manifests and metadata, then v
 	makefileBundleBuildPushFragment = `
 .PHONY: bundle-build
 bundle-build: ## Build the bundle image.
-	docker build -f bundle.Dockerfile -t $(BUNDLE_IMG) .
+	$(CONTAINER_TOOL) build -f bundle.Dockerfile -t $(BUNDLE_IMG) .
 
 .PHONY: bundle-push
 bundle-push: ## Push the bundle image.
@@ -303,7 +303,7 @@ endif
 # https://github.com/operator-framework/community-operators/blob/7f1438c/docs/packaging-operator.md#updating-your-existing-operator
 .PHONY: catalog-build
 catalog-build: opm ## Build a catalog image.
-	$(OPM) index add --container-tool docker --mode semver --tag $(CATALOG_IMG) --bundles $(BUNDLE_IMGS) $(FROM_INDEX_OPT)
+	$(OPM) index add --container-tool $(CONTAINER_TOOL) --mode semver --tag $(CATALOG_IMG) --bundles $(BUNDLE_IMGS) $(FROM_INDEX_OPT)
 
 # Push the catalog image.
 .PHONY: catalog-push