Use /usr/local/bin as default install location

rebar.mk

@@ -5,21 +5,29 @@ REBAR_GLOBAL ?= $(shell which rebar)
 REBAR_LOCAL  ?= $(shell which ./rebar)
 REBAR_TARGET ?= $(dir $(shell which escript))
 
+# Check for local rebar (./rebar), then globally installed and default to
+# /usr/local/bin/rebar
 ifneq ($(strip $(REBAR_LOCAL)), )
 REBAR ?= $(REBAR_LOCAL)
 else ifneq ($(strip $(REBAR_GLOBAL)), )
 REBAR ?= $(REBAR_GLOBAL)
 else
-REBAR ?= rebar
+REBAR ?= /usr/local/bin/rebar
 $(warning Rebar not installed or available. Try 'make rebar-info')
 endif
 
+# Try to use wget and fall back to curl
 ifneq ($(strip $(shell which wget)), )
 REBAR_FETCH ?= wget --no-check-certificate -q -O - $(REBAR_URL)
 else
 REBAR_FETCH ?= curl -s -f $(REBAR_URL)
 endif
 
+# Check for missing/empty REBAR_TARGET; fallback to /usr/local/bin in that
+# situation
+ifeq ($(strip $(REBAR_TARGET)),)
+REBAR_TARGET = /usr/local/bin
+endif
 
 rebar-info:
 	@echo "Rebar needs to be either on your path or present in the current" \