Allow overriding build version in Makefile (#57)

Author: bakhtin

Makefile

@@ -2,7 +2,7 @@
 # and Reth: https://github.com/paradigmxyz/reth/blob/main/Makefile
 .DEFAULT_GOAL := help
 
-VERSION := $(shell git describe --tags --always --dirty="-dev")
+VERSION ?= $(shell git describe --tags --always --dirty="-dev")
 
 ##@ Help