Disable annoying docker cli hints. Fix undefined var.

build-system/scripts/build_local

@@ -108,7 +108,7 @@ for E in "${PROJECTS[@]}"; do
     if [ -z "$NO_CACHE" ] && docker image ls --format "{{.Repository}}:{{.Tag}}" | grep -q -w "$CACHE_IMAGE_URI$"; then
       echo -e "${GREEN}Image exists locally. Tagging as $DEPLOY_IMAGE_URI${RESET}"
     else
-      if [ -n "$USE_CACHE" ] && image_exists $REPO $TAG ; then
+      if [ -n "${USE_CACHE:-}" ] && image_exists $REPO $TAG ; then
         docker pull $CACHE_IMAGE_URI
       else
         docker build ${ADDITIONAL_ARGS:-} --build-arg COMMIT_HASH=$COMMIT_HASH -f $DOCKERFILE -t $CACHE_IMAGE_URI .

build-system/scripts/setup_env

@@ -100,6 +100,7 @@ echo export DEPLOY_TAG=${DEPLOY_TAG:-} >> $BASH_ENV
 echo export BRANCH=$BRANCH >> $BASH_ENV
 echo export PULL_REQUEST=$PULL_REQUEST >> $BASH_ENV
 echo export DRY_DEPLOY=${DRY_DEPLOY:-0} >> $BASH_ENV
+echo export DOCKER_CLI_HINTS=false >> $BASH_ENV
 
 # We want very strict failures on any failing command, undefined variable, or commands that pipe to other commands.
 echo set -euo pipefail >> $BASH_ENV