feat(Dockerfile): mock ksops plugin for kustomize

In order for the pipeline to work with kustomize projects using ksops for encryption, we provide a mock plugin to kustomize. This will simply exit with status code 0 when called, thus effectively ignoring secrets and enabling the pipeline to deal with encrypted content without needing a key to decrypt it.

Dockerfile

@@ -12,5 +12,10 @@ RUN apk add --no-cache \
     && wget https://github.com/kubernetes-sigs/kustomize/releases/download/kustomize%2F${KUSTOMIZE_VERSION}/kustomize_${KUSTOMIZE_VERSION}_linux_amd64.tar.gz -O- | tar -xzf- \
     && wget https://storage.googleapis.com/kubernetes-release/release/${KUBECTL_VERSION}/bin/linux/amd64/kubectl \
     && chmod +x kustomize \
-    && chmod +x kubectl\
+    && chmod +x kubectl \
+    && mkdir -p /root/fakeplugins/viaduct.ai/v1/ksops-exec \
+    && printf "#!/bin/sh\nexit 0\n" > /root/fakeplugins/viaduct.ai/v1/ksops-exec/ksops-exec \
+    && chmod 755 /root/fakeplugins/viaduct.ai/v1/ksops-exec/ksops-exec \
     ;
+
+ENV KUSTOMIZE_PLUGIN_HOME=/root/fakeplugins