Add targets to copy artefacts from ghdl-formal image

.gitignore

@@ -0,0 +1,2 @@
+artefacts
+*.tar.gz

Makefile

@@ -1,4 +1,4 @@
-.PHONY: symbiyosys ghdl-formal all NOCACHE
+.PHONY: symbiyosys ghdl-formal all NOCACHE clean copy
 
 # Support for make environment variable NOCACHE
 ifeq (NOCACHE,$(lastword $(MAKECMDGOALS)))
@@ -18,8 +18,25 @@ else
     $(info INFO: Using user given tag '${TAG}')
 endif
 
+
 all: symbiyosys ghdl-formal
 
+copy: ghdl-formal_${TAG}.tar.gz
+
+
 .SECONDEXPANSION:
 symbiyosys ghdl-formal: $$@.Dockerfile
 	docker build ${OPTIONS} -t $@:${TAG} -f $@.Dockerfile .
+
+
+ghdl-formal_${TAG}.tar.gz:
+	mkdir -p artefacts
+	docker run --rm -dit --name=ghdl-dummy ghdl-formal:${TAG} > /dev/null
+	docker cp ghdl-dummy:/opt/. artefacts
+	docker rm -f ghdl-dummy > /dev/null
+	tar -C artefacts -czf ghdl-formal_${TAG}.tar.gz .
+
+
+clean:
+	rm -rf artefacts
+	rm -f ghdl-formal_*.tar.gz