Fix missing CGO_EXTRA_FLAGS build arg for docker (#11782)

Co-authored-by: zeripath <art27@cantab.net>

Dockerfile

@@ -9,6 +9,7 @@ ENV GOPROXY ${GOPROXY:-direct}
 ARG GITEA_VERSION
 ARG TAGS="sqlite sqlite_unlock_notify"
 ENV TAGS "bindata $TAGS"
+ARG CGO_EXTRA_CFLAGS
 
 #Build deps
 RUN apk --no-cache add build-base git nodejs npm

docker/Makefile

@@ -11,4 +11,4 @@ docker:
 
 .PHONY: docker-build
 docker-build:
-	docker run -ti --rm -v $(CURDIR):/srv/app/src/code.gitea.io/gitea -w /srv/app/src/code.gitea.io/gitea -e TAGS="bindata $(TAGS)" LDFLAGS="$(LDFLAGS)" webhippie/golang:edge make clean build
+	docker run -ti --rm -v $(CURDIR):/srv/app/src/code.gitea.io/gitea -w /srv/app/src/code.gitea.io/gitea -e TAGS="bindata $(TAGS)" LDFLAGS="$(LDFLAGS)" CGO_EXTRA_CFLAGS="$(CGO_EXTRA_CFLAGS)" webhippie/golang:edge make clean build