wire in weavetools image build

We use a plain ubuntu container as a build environment for ethtool &
conntrack, so a) we don't require onerous tooling on the build host,
and b) don't pollute the build host with build artefacts. The latter
arise because I can only get conntrack to build by installing its
dependencies 'globally'.

Th dir containing the build script is volume-mounted into the
container, and that is where we also expect to see the result, namely
a 'bin' sub-dir containing two executables.

The weavetools image is then constructed from the 'scratch' image and
contains just that dir.

Makefile

@@ -7,12 +7,15 @@ SUDO=sudo
 WEAVE_VERSION=git-$(shell git rev-parse --short=12 HEAD)
 WEAVER_EXE=weaver/weaver
 WEAVEDNS_EXE=weavedns/weavedns
+WEAVETOOLS_EXES=tools/bin
 WEAVER_IMAGE=zettio/weave
 WEAVEDNS_IMAGE=zettio/weavedns
+WEAVETOOLS_IMAGE=zettio/weavetools
 WEAVER_EXPORT=/var/tmp/weave.tar
 WEAVEDNS_EXPORT=/var/tmp/weavedns.tar
+WEAVETOOLS_EXPORT=/var/tmp/weavetools.tar
 
-all: $(WEAVER_EXPORT) $(WEAVEDNS_EXPORT)
+all: $(WEAVER_EXPORT) $(WEAVEDNS_EXPORT) $(WEAVETOOLS_EXPORT)
 
 $(WEAVER_EXE) $(WEAVEDNS_EXE):
 	go get -tags netgo ./$(shell dirname $@)
@@ -29,6 +32,9 @@ $(WEAVER_EXE) $(WEAVEDNS_EXE):
 $(WEAVER_EXE): router/*.go weaver/main.go
 $(WEAVEDNS_EXE): nameserver/*.go weavedns/main.go
 
+$(WEAVETOOLS_EXES): tools/build.sh
+	$(SUDO) docker run --rm -v $(realpath $(<D)):/home/weave ubuntu sh /home/weave/build.sh
+
 $(WEAVER_EXPORT): weaver/Dockerfile $(WEAVER_EXE)
 	$(SUDO) docker build -t $(WEAVER_IMAGE) weaver
 	$(SUDO) docker save $(WEAVER_IMAGE):latest > $@
@@ -37,10 +43,15 @@ $(WEAVEDNS_EXPORT): weavedns/Dockerfile $(WEAVEDNS_EXE)
 	$(SUDO) docker build -t $(WEAVEDNS_IMAGE) weavedns
 	$(SUDO) docker save $(WEAVEDNS_IMAGE):latest > $@
 
+$(WEAVETOOLS_EXPORT): tools/Dockerfile $(WEAVETOOLS_EXES)
+	$(SUDO) docker build -t $(WEAVETOOLS_IMAGE) tools
+	$(SUDO) docker save $(WEAVETOOLS_IMAGE):latest > $@
+
 # Add more directories in here as more tests are created
 tests:
 	cd nameserver; go test -tags netgo
 
 clean:
-	-$(SUDO) docker rmi $(WEAVER_IMAGE) $(WEAVEDNS_IMAGE)
-	rm -f $(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVER_EXPORT) $(WEAVEDNS_EXPORT)
+	-$(SUDO) docker rmi $(WEAVER_IMAGE) $(WEAVEDNS_IMAGE) $(WEAVETOOLS_IMAGE)
+	rm -f $(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVER_EXPORT) $(WEAVEDNS_EXPORT) $(WEAVETOOLS_EXPORT)
+	$(SUDO) rm -rf $(WEAVETOOLS_EXES)