simplify dependencies

This isn't as precise, but these common dependencies rarely change.

Makefile

@@ -40,7 +40,7 @@ travis: $(EXES)
 update: $(EXES)
 	go get -u -f -v -tags -netgo $(addprefix ./,$(dir $(EXES)))
 
-$(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE): common/*.go
+$(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE): common/*.go common/*/*.go net/*.go
 	go get -tags netgo ./$(@D)
 	go build -ldflags "-extldflags \"-static\" -X main.version $(WEAVE_VERSION)" -tags netgo -o $@ ./$(@D)
 	@strings $@ | grep cgo_stub\\\.go >/dev/null || { \
@@ -52,10 +52,10 @@ $(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE): common/*.go
 		false; \
 	}
 
-$(WEAVER_EXE): router/*.go ipam/*.go ipam/*/*.go common/*.go common/*/*.go net/*.go weaver/main.go
-$(WEAVEDNS_EXE): nameserver/*.go common/*.go common/*/*.go net/*.go weavedns/main.go
-$(WEAVEPROXY_EXE): proxy/*.go common/*.go weaveproxy/main.go
-$(WEAVEWAIT_EXE): weavewait/*.go net/*.go weavewait/main.go
+$(WEAVER_EXE): router/*.go ipam/*.go ipam/*/*.go weaver/main.go
+$(WEAVEDNS_EXE): nameserver/*.go weavedns/main.go
+$(WEAVEPROXY_EXE): proxy/*.go weaveproxy/main.go
+$(WEAVEWAIT_EXE): weavewait/*.go weavewait/main.go
 
 # Sigproxy needs separate rule as it fails the netgo check in the main
 # build stanza due to not importing net package