[Compose] Allow to set repository in docker-compose.override.yml

helper-scripts/docker-compose.override.yml.d/BUILD_FLAGS/docker-compose.override.yml

@@ -13,7 +13,11 @@ services:
     build: ./data/Dockerfiles/phpfpm
 
   sogo-mailcow:
-    build: ./data/Dockerfiles/sogo
+    build:
+      context: ./data/Dockerfiles/sogo
+      dockerfile: Dockerfile
+      args:
+        - SOGO_DEBIAN_REPOSITORY=http://packages.inverse.ca/SOGo/nightly/4/debian/
 
   dovecot-mailcow:
     build: ./data/Dockerfiles/dovecot