Adding an emptyDir to kubernetes deployment

This should resolve the out-of-disk problems reported in #379

containers/buildkite-premerge-debian/Dockerfile

@@ -12,5 +12,8 @@ RUN chmod og+rx /usr/local/bin/*.sh
 COPY --chown=buildkite-agent:buildkite-agent pre-checkout /etc/buildkite-agent/hooks
 COPY --chown=buildkite-agent:buildkite-agent post-checkout /etc/buildkite-agent/hooks
 
+# buildkite working directory
+VOLUME /var/lib/buildkite-agent
+
 ENTRYPOINT ["entrypoint.sh"]
 CMD ["gosu", "buildkite-agent", "buildkite-agent", "start", "--no-color"]

kubernetes/buildkite/linux-agents.yaml

@@ -45,6 +45,8 @@ spec:
           volumeMounts:
             - name: github-ssh
               mountPath: /mnt/ssh
+            - name: workdir
+              mountPath: /var/lib/buildkite-agent
           env:
             - name: BUILDKITE_AGENT_TOKEN
               valueFrom:
@@ -73,6 +75,8 @@ spec:
         - name: github-ssh
           secret:
             secretName: github-ssh
+        - name: workdir
+          emptyDir: {}
       nodeSelector:
         cloud.google.com/gke-nodepool: linux-agents-2
       terminationGracePeriodSeconds: 3600