Improve MTAR build process in Makefile

 - Add variable for MTAR filename with versioning
 - Update build command to use the new MTAR_FILENAME variable
 - Change destination path for the built MTAR file
 - Fix typo in build message

src/autoscaler/Makefile

@@ -5,6 +5,7 @@ aes_terminal_font_yellow := \e[38;2;255;255;0m
 aes_terminal_reset := \e[0m
 VERSION ?= 0.0.0-rc.1
 DEST ?= build
+MTAR_FILENAME ?= app-autoscaler-release-v$(VERSION).mtar
 
 GO_VERSION = $(shell go version | sed -e 's/^[^0-9.]*\([0-9.]*\).*/\1/')
 GO_DEPENDENCIES = $(shell find . -type f -name '*.go')
@@ -172,12 +173,12 @@ mta-logs:
 
 .PHONY: mta-build
 mta-build: mta-build-clean
-	@echo "bulding mtar file for version: $(VERSION)"
+	@echo "building mtar file for version: $(VERSION)"
 	cp mta.tpl.yaml mta.yaml
 	sed -i 's/VERSION/$(VERSION)/g' mta.yaml
 	mkdir -p $(DEST)
-	mbt build
-	@mv mta_archives/com.github.cloudfoundry.app-autoscaler-release_$(VERSION).mtar $(DEST)/app-autoscaler-release-v$(VERSION).mtar
+	mbt build -t /tmp --mtar $(MTAR_FILENAME)
+	@mv /tmp/$(MTAR_FILENAME) $(DEST)/$(MTAR_FILENAME)
 
 mta-build-clean:
 	rm -rf mta_archives