Make the version within makefile overwriteable (#6080)

Fix #1173

Makefile

@@ -25,14 +25,14 @@ EXTRA_GOFLAGS ?=
 
 ifneq ($(DRONE_TAG),)
 	VERSION ?= $(subst v,,$(DRONE_TAG))
-	GITEA_VERSION := $(VERSION)
+	GITEA_VERSION ?= $(VERSION)
 else
 	ifneq ($(DRONE_BRANCH),)
 		VERSION ?= $(subst release/v,,$(DRONE_BRANCH))
 	else
 		VERSION ?= master
 	endif
-	GITEA_VERSION := $(shell git describe --tags --always | sed 's/-/+/' | sed 's/^v//')
+	GITEA_VERSION ?= $(shell git describe --tags --always | sed 's/-/+/' | sed 's/^v//')
 endif
 
 LDFLAGS := -X "main.Version=$(GITEA_VERSION)" -X "main.Tags=$(TAGS)"