Fix Docker builds.

Thanks to xet7 !

Dockerfile

@@ -4,6 +4,8 @@ LABEL maintainer="wekan"
 # Set the environment variables (defaults where required)
 # DOES NOT WORK: paxctl fix for alpine linux: https://github.com/wekan/wekan/issues/1303
 # ENV BUILD_DEPS="paxctl"
+ARG DEBIAN_FRONTEND=noninteractive
+
 ENV BUILD_DEPS="apt-utils libarchive-tools gnupg gosu wget curl bzip2 g++ build-essential git ca-certificates python3" \
     DEBUG=false \
     NODE_VERSION=v12.16.2 \