Add support for Podman as well as Docker (#1026)

Would like to see this package work on systems without Docker installed
which have Podman.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Makefile

@@ -2,6 +2,7 @@ MAKEFLAGS += --warn-undefined-variables
 SHELL := /bin/bash
 .SHELLFLAGS := -o pipefail -euc
 .DEFAULT_GOAL := install
+ENGINE := $(shell { command -v podman || command -v docker; } 2>/dev/null)
 
 include Makefile.variables
 
@@ -33,7 +34,7 @@ clean:
 
 ## prefix before other make targets to run in your local dev environment
 local: | quiet
-	@$(eval DOCKRUN= )
+	@$(eval ENGINERUN= )
 	@mkdir -p tmp
 	@touch tmp/dev_image_id
 quiet: # this is silly but shuts up 'Nothing to be done for `local`'
@@ -42,9 +43,9 @@ quiet: # this is silly but shuts up 'Nothing to be done for `local`'
 prepare: tmp/dev_image_id
 tmp/dev_image_id: Dockerfile.dev scripts/devtools.sh
 	@mkdir -p tmp
-	@docker rmi -f ${DEV_IMAGE} > /dev/null 2>&1 || true
-	@docker build -t ${DEV_IMAGE} -f Dockerfile.dev .
-	@docker inspect -f "{{ .ID }}" ${DEV_IMAGE} > tmp/dev_image_id
+	@${ENGINE} rmi -f ${DEV_IMAGE} > /dev/null 2>&1 || true
+	@${ENGINE} build -t ${DEV_IMAGE} -f Dockerfile.dev .
+	@${ENGINE} inspect -f "{{ .ID }}" ${DEV_IMAGE} > tmp/dev_image_id
 
 # ----------------------------------------------
 # build
@@ -54,60 +55,61 @@ build: build/dev
 .PHONY: build/dev
 build/dev: test *.go
 	@mkdir -p bin/
-	${DOCKRUN} go build --ldflags "$(LDFLAGS)"
-	${DOCKRUN} bash ./scripts/acceptance.sh
+	${ENGINERUN} go build --ldflags "$(LDFLAGS)"
+	${ENGINERUN} bash ./scripts/acceptance.sh
 
 ## Compile the project for multiple OS and Architectures.
 xcompile: check
 	@rm -rf build/
 	@mkdir -p build
-	${DOCKRUN} bash ./scripts/xcompile.sh
+	${ENGINERUN} bash ./scripts/xcompile.sh
 	@find build -type d -exec chmod 755 {} \; || :
 	@find build -type f -exec chmod 755 {} \; || :
 
 .PHONY: install
 install: build
-	${DOCKRUN} go install
+	${ENGINERUN} go install
 
 # Each of the fetch should be an entry within vendor.json; not currently included within project
 .PHONY: vendor
 vendor: tmp/dev_image_id
-	${DOCKRUN} go mod vendor
+	@mkdir -p vendor
+	${ENGINERUN} go mod vendor
 
 # ----------------------------------------------
 # develop and test
 
 .PHONY: format
 format: vendor
-	${DOCKRUN} bash ./scripts/format.sh
+	${ENGINERUN} bash ./scripts/format.sh
 
 
 .PHONY: secure
 secure: format
-	${DOCKRUN} bash ./scripts/secure.sh
+	${ENGINERUN} bash ./scripts/secure.sh
 
 .PHONY: check
 check: secure
-	${DOCKRUN} bash ./scripts/check.sh
+	${ENGINERUN} bash ./scripts/check.sh
 
 
 
 .PHONY: test
 test: check
-	${DOCKRUN} bash ./scripts/test.sh
+	${ENGINERUN} bash ./scripts/test.sh
 
 .PHONY: cover
 cover: check
 	@rm -rf cover/
 	@mkdir -p cover
-	${DOCKRUN} bash ./scripts/coverage.sh
+	${ENGINERUN} bash ./scripts/coverage.sh
 	@find cover -type d -exec chmod 755 {} \; || :
 	@find cover -type f -exec chmod 644 {} \; || :
 
 
 .PHONY: release
 release: xcompile
-	${DOCKRUN} bash ./scripts/publish.sh
+	${ENGINERUN} bash ./scripts/publish.sh
 
 # ----------------------------------------------
 # utilities