Fix install target on OSX (see redis#495)

pietern · antirez · commit f16d090c728d · 2012-05-15T11:18:50.000+02:00
diff --git a/Makefile b/Makefile
@@ -5,3 +5,7 @@ default: all
 .DEFAULT:
 	cd src && $(MAKE) $@
 
+install:
+	cd src && $(MAKE) $@
+
+.PHONY: install
