Makefile: Add signature support (requires ecdsautils)

Makefile

@@ -2,6 +2,8 @@ GLUON_BUILD_DIR := gluon-build
 GLUON_GIT_URL := git://github.com/freifunk-gluon/gluon.git
 GLUON_GIT_REF := v2014.4
 
+SECRET_KEY_FILE ?= ${HOME}/.gluon-secret-key
+
 _GIT_DESCRIBE = $(shell git describe --tags 2>/dev/null)
 ifneq (,${_GIT_DESCRIBE})
   GLUON_RELEASE := ${_GIT_DESCRIBE}
@@ -16,22 +18,25 @@ GLUON_MAKE := ${MAKE} -j ${JOBS} -C ${GLUON_BUILD_DIR} \
                       GLUON_RELEASE=${GLUON_RELEASE} \
                       GLUON_BRANCH=${GLUON_BRANCH}
 
-all: build
+all: build manifest
 
 build: gluon-prepare
 	echo '${GLUON_RELEASE} (${GLUON_BRANCH})'
-	${GLUON_MAKE} update
 	${GLUON_MAKE}
 
 manifest: gluon-prepare
 	${GLUON_MAKE} manifest
 
+sign: manifest
+	gluon-build/contrib/sign.sh ${SECRET_KEY_FILE} gluon-build/images/sysupgrade/${GLUON_BRANCH}.manifest
+
 ${GLUON_BUILD_DIR}:
 	git clone ${GLUON_GIT_URL} ${GLUON_BUILD_DIR}
 
 gluon-prepare: ${GLUON_BUILD_DIR}
 	(cd ${GLUON_BUILD_DIR} && git fetch origin && git checkout -q ${GLUON_GIT_REF})
 	ln -sfT .. ${GLUON_BUILD_DIR}/site
+	${GLUON_MAKE} update
 
 clean:
 	rm -rf ${GLUON_BUILD_DIR}