Build Erlang if it is not present on the host

.gitignore

@@ -1,3 +1,5 @@
+.kerl
+erlang
 deps
 log
 apps/htoad/ebin

Makefile

@@ -1,11 +1,27 @@
+HERE=$(shell pwd)
+KERL_CONFIG_OPTS=""
+
+ifeq ($(shell which erl),)
+	ERL=erlang/bin/erl
+	REBAR=". $(HERE)/erlang/activate && ./rebar"
+else
+	ERL=$(shell which erl)
+	REBAR="./rebar"
+endif
+
 all: release
 
-release: compile
+release: $(ERL) compile
 		@rm -rf rel/htoad
-		@./rebar generate
+		@$(REBAR) generate
+
+compile: $(ERL) deps
+		@$(REBAR) compile
+
+deps: $(ERL)
+		@$(REBAR) get-deps
 
-compile: deps
-		@./rebar compile
+$(ERL):
+		@KERL_CONFIGURE_OPTIONS=$(KERL_CONFIG_OPTS) KERL_INSTALL_AGNERIZED_REBAR=n HOME=$(HERE) ./kerl build R15B r15b
+		@KERL_CONFIGURE_OPTIONS=$(KERL_CONFIG_OPTS) KERL_INSTALL_AGNERIZED_REBAR=n HOME=$(HERE) ./kerl install r15b erlang
 
-deps:
-		@./rebar get-deps