update syntax against go1.6

Author: msagheer

Makefile

@@ -7,7 +7,7 @@ PLUGIN_VERSION=git-$(shell git rev-parse --short=12 HEAD)
 
 $(PLUGIN_EXE): plugin/main.go plugin/driver/*.go
 	go get -tags netgo ./$(@D)
-	go build -ldflags "-extldflags \"-static\" -X main.version $(PLUGIN_VERSION)" -tags netgo -o $@ ./$(@D)
+	go build -ldflags "-extldflags \"-static\" -X main.version=$(PLUGIN_VERSION)" -tags netgo -o $@ ./$(@D)
 	@strings $@ | grep cgo_stub\\\.go >/dev/null || { \
 		rm $@; \
 		echo "\nGo standard library is built without the 'netgo' build tag."; \