fix(build) fix local build

docker build is now an alias for docker buildx, so we need to load the
images in order for the next steps to work since images rely on
previously built images.

Makefile

@@ -33,8 +33,9 @@ $(addprefix buildx_,$(JITSI_SERVICES)):
 	$(MAKE) --no-print-directory JITSI_SERVICE=$(patsubst buildx_%,%,$@) buildx
 
 build:
-	docker build \
+	docker buildx build \
 		$(BUILD_ARGS) \
+		--load \
 		--progress plain \
 		--tag $(JITSI_REPO)/$(JITSI_SERVICE) \
 		$(JITSI_SERVICE)