terraform deployer: silent gcloud SDK installation

Reduce output from gcloud SDK installation process, by silencing the
various steps.

This is needed to reduce image build log verbosity; gcloud SDK
installation output is also difficult to read on terminal that do not
support colours.

internal/install/_static/Dockerfile.terraform_deployer

@@ -2,15 +2,15 @@ FROM hashicorp/terraform:light as terraform
 
 FROM python:3-alpine
 
-# required by gcloud SDK
 RUN apk add --no-cache git openssh curl
 
+# Announcements for new releases: https://groups.google.com/g/google-cloud-sdk-announce
 ENV GCLOUD_SDK_VERSION 369.0.0
 ENV PATH $PATH:/usr/local/gcloud/google-cloud-sdk/bin
-RUN curl "https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/google-cloud-sdk-$GCLOUD_SDK_VERSION-linux-x86_64.tar.gz" > /tmp/google-cloud-sdk.tar.gz \
+RUN curl --silent "https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/google-cloud-sdk-$GCLOUD_SDK_VERSION-linux-x86_64.tar.gz" > /tmp/google-cloud-sdk.tar.gz \
   && mkdir -p /usr/local/gcloud \
-  && tar -C /usr/local/gcloud -xvf /tmp/google-cloud-sdk.tar.gz \
-  && /usr/local/gcloud/google-cloud-sdk/install.sh -q --override-components="bq" \
+  && tar -C /usr/local/gcloud -xf /tmp/google-cloud-sdk.tar.gz \
+  && /usr/local/gcloud/google-cloud-sdk/install.sh -q --override-components="bq" &>/dev/null \
   && rm /tmp/google-cloud-sdk.tar.gz
 
 HEALTHCHECK --timeout=3s CMD sh -c "[ -f /tmp/tf-applied ]"