fix: goreleaser fips mode docker login cred passing

Part of https://gitlab.com/gitlab-com/gl-infra/gitlab-dedicated/team/-/issues/1312

Unfortunately due to the way permissons and volumes work in our CI Setup, it's best
if we use `docker login` inside the goreleaser container, and to do that we need to
pass a json file in a specific structure they require into the container.

As described at https://gitlab.com/gitlab-org/gitlab-foss/-/issues/41227#note_52029664
we have to pass this file somewhere under `/builds`. However, it can't be in the current working directory,
otherwise goreleaser complains about Git being in a dirty state (extra files not in Git)
https://goreleaser.com/errors/dirty/.

goreleaser.yml

@@ -69,9 +69,6 @@ goreleaser-fips:
   services:
     - docker:dind
   variables:
-    DOCKER_REGISTRY: $CI_REGISTRY
-    DOCKER_USERNAME: $CI_REGISTRY_USER
-    DOCKER_PASSWORD: $CI_REGISTRY_PASSWORD
     GIT_DEPTH: 0
   rules:
@@ -85,16 +82,26 @@ goreleaser-fips:
     ----------------------------------------------------------
     Running go-releaser in fips mode
     EOD
-    echo "$CI_REGISTRY_PASSWORD" | docker login "$CI_REGISTRY" -u "$CI_REGISTRY_USER" --password-stdin
+    mkdir -p /builds/shared
+    cat > /builds/shared/docker-creds.json <<-EOF
+    {
+      "registries": [
+        {
+          "user": "$CI_REGISTRY_USER",
+          "pass": "$CI_REGISTRY_PASSWORD",
+          "registry": "$CI_REGISTRY"
+        }
+      ]
+    }
+    EOF
     docker run --rm --privileged \
       -v $PWD:$PWD \
       -w $PWD \
       -v /var/run/docker.sock:/var/run/docker.sock \
-      -v $HOME/.docker/config.json:/root/.docker/config.json \
-      -e DOCKER_USERNAME -e DOCKER_PASSWORD -e DOCKER_REGISTRY  \
+      -v /builds/shared/docker-creds.json:/docker-creds.json \
       -e GITLAB_TOKEN -e CI_REGISTRY_IMAGE \
       -e CI_SERVER_URL \
-      -e GL_ASDF_GORELEASER_VERSION \
+      -e DOCKER_CREDS_FILE=/docker-creds.json \
       ${GORELEASER_DOCKER_EXTRA_ARGS:-} \
       goreleaser/goreleaser-cross:v${GL_ASDF_GOLANG_VERSION}-v${GL_ASDF_GORELEASER_VERSION} release --rm-dist ${GORELEASER_EXTRA_ARGS:-}
   after_script: |