Expose libbeat version in generated beats (#6345)

* set libbeat version

* don't shadow config import

* switch cfg var per feedback

cfg is normally used to represent go-ucfg / common.Config

generator/beat/{beat}/Makefile

@@ -8,6 +8,7 @@ ES_BEATS?=./vendor/github.com/elastic/beats
 GOPACKAGES=$(shell govendor list -no-status +local)
 PREFIX?=.
 NOTICE_FILE=NOTICE
+GOBUILD_FLAGS=-i -ldflags "-X $(BEAT_PATH)/vendor/github.com/elastic/beats/libbeat/version.buildTime=$(NOW) -X $(BEAT_PATH)/vendor/github.com/elastic/beats/libbeat/version.commit=$(COMMIT_ID)"
 
 # Path to the libbeat Makefile
 -include $(ES_BEATS)/libbeat/scripts/Makefile

generator/beat/{beat}/beater/{beat}.go.tmpl

@@ -19,14 +19,14 @@ type {Beat} struct {
 
 // Creates beater
 func New(b *beat.Beat, cfg *common.Config) (beat.Beater, error) {
-	config := config.DefaultConfig
-	if err := cfg.Unpack(&config); err != nil {
+	c := config.DefaultConfig
+	if err := cfg.Unpack(&c); err != nil {
 		return nil, fmt.Errorf("Error reading config file: %v", err)
 	}
 
 	bt := &{Beat}{
 		done:   make(chan struct{}),
-		config: config,
+		config: c,
 	}
 	return bt, nil
 }