fix Docker build warnings of LegacyKeyValueFormat

Author: deminy

Dockerfile.cli.twig

@@ -1,10 +1,10 @@
 FROM php:{{ php_version }}-cli
 
-ENV DEBIAN_FRONTEND noninteractive
-ENV TERM xterm-color
+ENV DEBIAN_FRONTEND=noninteractive
+ENV TERM=xterm-color
 
 ARG DEV_MODE
-ENV DEV_MODE $DEV_MODE
+ENV DEV_MODE=$DEV_MODE
 
 COPY --from=composer:{{ composer.version }} /usr/bin/composer /usr/bin/
 COPY ./rootfilesystem/ /