Fix Cloudbuild $HOME override, update Earthfile to 0.7

Earthfile

@@ -1,3 +1,7 @@
+VERSION 0.8
+
+PROJECT earthly-technologies/cloud
+
 FROM golang:1.16-alpine3.13
 WORKDIR /go-example
 
@@ -25,4 +29,4 @@ docker:
 # Demo for Google Cloud Build, showing use of a dedicated service account
 gcp-cloudbuild:
     FROM gcr.io/cloud-builders/gsutil
-    RUN --mount type=secret,id=+secrets/earthly-technologies/google/cloudbuild-service-key,target=/root/key.json gcloud auth activate-service-account --key-file=/root/key.json && gsutil ls -p earthly-jupyterlab
+    RUN --mount type=secret,id=google/cloudbuild-service-key,target=/root/key.json gcloud auth activate-service-account --key-file=/root/key.json && gsutil ls -p earthly-jupyterlab

cloudbuild.yaml

@@ -1,18 +1,35 @@
 steps:
   - id: 'build'
-    name: 'earthly/earthly:v0.5.24'
+    name: 'earthly/earthly:v0.8.7'
+    env:
+      - "HOME=/root"
     args:
       - --allow-privileged
+      - --ci
+      # - --push # Uncomment to allow GCP to push images to your choice of repository. Secrets for your repository must be configured.
       - +docker
 
+  - id: 'secrets'
+    name: 'earthly/earthly:v0.8.7'
+    env:
+      - "HOME=/root"
+      - "EARTHLY_PROJECT=cloud"
+    args:
+      - secrets
+      - ls
+    secretEnv:
+      - 'EARTHLY_TOKEN'
+
   - id: 'gcp-test'
-    name: 'earthly/earthly:v0.5.24'
+    name: 'earthly/earthly:v0.8.7'
+    env:
+      - "HOME=/root"
     args:
       - +gcp-cloudbuild
     secretEnv:
       - 'EARTHLY_TOKEN'
 
 availableSecrets:
   secretManager:
-  - versionName: projects/earthly-jupyterlab/secrets/EARTHLY_TOKEN/versions/2
+  - versionName: projects/earthly-jupyterlab/secrets/EARTHLY_TOKEN/versions/4
     env: 'EARTHLY_TOKEN'