erlang: add Makefile and rebar.config for building with rebar3

erlang/Makefile

@@ -0,0 +1,35 @@
+REBAR3=$(shell type -p rebar3 || echo ./rebar3)
+REBAR3_GIT=https://github.com/erlang/rebar3.git
+REBAR3_VSN=3.7.5
+
+PROGRAMS=8to9
+
+default: compile link
+
+compile:	$(REBAR3)
+	$(REBAR3) compile
+
+link:	$(REBAR3)
+	for PROG in $(PROGRAMS); do \
+		rm -f _build/$$PROG; \
+		ln -s default _build/$$PROG; \
+		$(REBAR3) as $$PROG escriptize; \
+	done
+
+distclean realclean:	clean
+	rm -f ./rebar3
+
+clean:	$(REBAR3)
+	$(REBAR3) clean
+	rm -rf _build
+
+./rebar3:
+	mkdir -p _build; \
+	cd _build; \
+	git clone --quiet $(REBAR3_GIT); \
+	cd rebar3; \
+	git checkout --quiet $(REBAR3_VSN); \
+	./bootstrap; \
+	mv rebar3 ../../; \
+	cd ../..; \
+	rm -rf _build/rebar3