Reprepare OpenWRT by default on make

Makefile

@@ -2,7 +2,9 @@ GLUONDIR:=${CURDIR}
 
 LN_S:=ln -sf
 
-all: images
+all:
+	$(MAKE) prepare
+	$(MAKE) images
 
 include $(GLUONDIR)/builder/gluon.mk
 

README.md

@@ -4,9 +4,9 @@ To build Gluon, use the following commands after checking out the repository:
     git clone git://github.com/freifunk-gluon/site-ffhl.git site # Get the Freifunk Lübeck site repository - or use your own!
     make                                                         # Build Gluon
 
-When building Gluon for the first time, the OpenWRT build environment is prepared. To update the OpenWRT
-environment, e. g. to compile added or changed packages, just use:
+When calling make, the OpenWRT build environment is prepared/updated. To rebuilt
+the images only, just use:
 
-    make prepare
+    make images
 
 The built images can be found in the directory /images.