Fix docker tag sanitizer

Use a `-` instead of `_` to make the docker tag also pass semver checks.

Signed-off-by: SuperQ <superq@gmail.com>

Makefile.common

@@ -91,7 +91,7 @@ BUILD_DOCKER_ARCHS = $(addprefix common-docker-,$(DOCKER_ARCHS))
 PUBLISH_DOCKER_ARCHS = $(addprefix common-docker-publish-,$(DOCKER_ARCHS))
 TAG_DOCKER_ARCHS = $(addprefix common-docker-tag-latest-,$(DOCKER_ARCHS))
 
-SANITIZED_DOCKER_IMAGE_TAG := $(subst +,_,$(DOCKER_IMAGE_TAG))
+SANITIZED_DOCKER_IMAGE_TAG := $(subst +,-,$(DOCKER_IMAGE_TAG))
 
 ifeq ($(GOHOSTARCH),amd64)
         ifeq ($(GOHOSTOS),$(filter $(GOHOSTOS),linux freebsd darwin windows))