makefile: {build,compose build} w/ buildkit

* faster builds with buildkit
  ref: https://www.docker.com/blog/faster-builds-in-compose-thanks-to-buildkit-support/
* use $(dcmd) variable at all times

* [skip ci]

Makefile

@@ -1,4 +1,5 @@
 dc = docker-compose
+dccmd = COMPOSE_DOCKER_CLI_BUILD=1 DOCKER_BUILDKIT=1 docker-compose
 dtag = netcoreultimateapp-prod
 dtagdev = netcoreultimapp-dev
 dfile = Dockerfile
@@ -6,7 +7,7 @@ dfiledev = $(dfile).dev
 lport = 8000
 lportdev = 8001
 CC = dotnet
-dcmd = docker
+dcmd = DOCKER_BUILDKIT=1 docker
 pruneargs = system prune -af
 dcmdrun = $(dcmd) run --rm
 wdir = /src
@@ -42,13 +43,13 @@ releasebuild: restore clean
 	$(CC) publish -c Release
 
 dockerbuild:
-	docker build \
+	$(dcmd) build \
 		--build-arg VCS_REF=`git rev-parse --short HEAD` \
 		--build-arg BUILD_DATE=`date -u +"%Y-%m-%dT%H:%M:%SZ"` \
 		-t $(dtag) -f $(dfile) --no-cache .
 
 dockerdevbuild:
-	docker build \
+	$(dcmd) build \
 		--build-arg VCS_REF=`git rev-parse --short HEAD` \
 		--build-arg BUILD_DATE=`date -u +"%Y-%m-%dT%H:%M:%SZ"` \
 		-t $(dtagdev) -f $(dfiledev) --no-cache .
@@ -66,19 +67,19 @@ dockerdevrun:
 	$(dcmdrun) -p $(lportdev):5000 $(dtagdev)
 
 dcdevb:
-	$(dc) -f $(dc).yml build --no-cache --pull --progress tty
+	$(dccmd) -f $(dc).yml build --no-cache --pull --progress tty
 
 dcprodbuild:
-	$(dc) -f $(dc).prod.yml build --no-cache --pull --progress tty
+	$(dccmd) -f $(dc).prod.yml build --no-cache --pull --progress tty
 
 dcdevup:
 	@echo ======================
 	@echo local dev port: $(lportdev)
 	@echo ======================
-	$(dc) -f $(dc).yml up --remove-orphans
+	$(dccmd) -f $(dc).yml up --remove-orphans
 
 dcprodup:
-	$(dc) -f $(dc).prod.yml up --remove-orphans --scale netcoreultimateapp-prod=2
+	$(dccmd) -f $(dc).prod.yml up --remove-orphans --scale netcoreultimateapp-prod=2
 
 kaniko:
 	$(krelease)