Update install/build-docker-images.sh

Fix in the case where vars are empty

Author: chadwhitacre

install/build-docker-images.sh

@@ -3,8 +3,8 @@ echo "${_group}Building and tagging Docker images ..."
 echo ""
 # Build any service that provides the image sentry-self-hosted-local first,
 # as it is used as the base image for sentry-cleanup-self-hosted-local.
-$dc build --build-arg http_proxy=$http_proxy --build-arg https_proxy=$https_proxy --build-arg no_proxy=$no_proxy --force-rm web
-$dc build --build-arg http_proxy=$http_proxy --build-arg https_proxy=$https_proxy --build-arg no_proxy=$no_proxy --force-rm
+$dc build --build-arg "http_proxy=${http_proxy:-}" --build-arg "https_proxy=${https_proxy:-}" --build-arg "no_proxy=${no_proxy:-}" --force-rm web
+$dc build --build-arg "http_proxy=${http_proxy:-}" --build-arg "https_proxy=${https_proxy:-}" --build-arg "no_proxy=${no_proxy:-}" --force-rm
 echo ""
 echo "Docker images built."