Add support for build-time http(s) proxy setting.

Dockerfile

@@ -1,5 +1,8 @@
 FROM alpine
 
+ARG http_proxy
+ARG https_proxy
+
 RUN apk add --no-cache openldap openldap-clients openldap-back-ldap openldap-overlay-deref ldapvi && mkdir -p /run/openldap
 
 COPY root /

docker-compose.yml

@@ -4,6 +4,9 @@ services:
   ldap.proxy:
     build:
       context: .
+      args:
+        http_proxy: ${http_proxy}
+        https_proxy: ${https_proxy}
     container_name: ldap.proxy
     networks:
       - ldap.proxy