Reduce memory usage by using a disk for buildkit's backing.

.webhook_bridge/pipeline-build-homepage-staging.yaml

@@ -155,6 +155,8 @@ spec:
         workspaces:
           - name: source
             workspace: git-source
+          - name: buildkitd
+            workspace: buildkit-cache
           - name: dockerconfig
             workspace: docker-credentials
         runAfter:
@@ -220,6 +222,7 @@ spec:
             value: "https://tekton.fizz.buzz/#/namespaces/$(context.pipelineRun.namespace)/pipelineruns/$(context.pipelineRun.name)"
     workspaces:
       - name: git-source
+      - name: buildkit-cache
       - name: docker-credentials
   workspaces:
     - name: git-source
@@ -231,7 +234,17 @@ spec:
           resources:
             requests:
               storage: 10Gi
-      subPath: rust-source
+      subPath: git-source
+    - name: buildkit-cache
+      volumeClaimTemplate:
+        spec:
+          storageClassName: "nfs-client"
+          accessModes:
+            - ReadWriteOnce
+          resources:
+            requests:
+              storage: 10Gi
+      subPath: builtkit-cache
     - name: docker-credentials
       secret:
         secretName: harbor-plain